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Seasonality and seasonal affective disorder (SAD): An evolutionary viewpoint tied to energy conservation and reproductive cycles
Abstract
The characteristic symptoms of SAD, including hypersomnia and weight gain, might reflect a genetically programmed attempt to conserve energy during historically predictable periods of dwindling food supply. While this basic hypothesis has obvious conceptual appeal, few authors have considered the specific positive selection pressures that might have contributed to such a process. The goal of the current paper is to further develop an evolutionary model of SAD with a focus on energy conservation in the context of seasonal reproductive cycles. To accomplish this, seasonal data on birth rates are considered from an evolutionary viewpoint. There is considerable indirect evidence that in temperate climates, the symptoms of SAD reflect a predisposition for conception to occur in late spring/early summer to ensure a peak of births in the late winter/early spring. The adaptive value of such a pattern, and its putative role in natural selection in humans, is also discussed.
... Second, and most crucially, the winter blues account requires that people whose seasonal depression is not mitigated by light irides leave fewer or less fertile offspring, but there is no indication they do or they might. Quite on the opposite, several lines of indirect evidence suggest that, as people migrated away from the equator and toward regions where food availability varied greatly during the year, the hibernationlike pattern of seasonal depression evolved precisely because it brought forth reproductive advantages (Davis and Levitan, 2005;Eagles, 2004). The psychological and behavioral impairments that accompany the dim days of fall and winter-including lowered enthusiasm for sex-remit, or even revert, during the bright days of spring and summer. ...
... The psychological and behavioral impairments that accompany the dim days of fall and winter-including lowered enthusiasm for sex-remit, or even revert, during the bright days of spring and summer. So, women of childbearing age (among which SAD is far more common than in older women or in men: Davis and Levitan, 2005) would be more likely to become pregnant in early summer and give birth in early spring-when, with warmer temperatures and heftier food supplies ahead, babies would have higher chances of surviving (Eagles, 2004). Indeed, the very symptoms of SAD (diminished energy, activity, and sociality; increased appetite, weight gain, and sleep) correspond to, and would favor, the natural changes associated with pregnancy (Davis and Levitan, 2005). ...
... So, women of childbearing age (among which SAD is far more common than in older women or in men: Davis and Levitan, 2005) would be more likely to become pregnant in early summer and give birth in early spring-when, with warmer temperatures and heftier food supplies ahead, babies would have higher chances of surviving (Eagles, 2004). Indeed, the very symptoms of SAD (diminished energy, activity, and sociality; increased appetite, weight gain, and sleep) correspond to, and would favor, the natural changes associated with pregnancy (Davis and Levitan, 2005). ...
A surprising number of humans are equipped with a subpar eye model—featuring pale, colorful irides that are nowhere as good as the original dark ones at guarding the retina from sunlight and do, in fact, raise one’s risk of eye disease. Here I apply evolutionary theory to understand why. I propose that the allele for human blue eyes, which arose just once, managed to spread from one individual to millions at an astonishing speed because it is a greenbeard. “Greenbeards”—imaginary genes, or groups of genes, that produce both a green beard and a behavior that favors other bearers of a green beard—have been deemed exceedingly unlikely to show up in the real world. And yet, as individuals who prefer blue eyes are more inclined to mate with blue-eyed partners and invest in blue-eyed offspring, any blue-eye preference (whether random or arising from the bias for colorful stimuli shared by all recognition systems) becomes rapidly linked to the blue-eye trait. Thus, blue eyes gain an edge by working like a peacock’s colorful tail and a nestling’s colorful mouth: twice self-reinforcing, “double runaway” evolution via sexual and parental selection. The blue-eye ornament gene, by binding to a behavior that favors other bearers of the blue-eye ornament gene, is ultimately recognizing and helping copies of itself in both kin and strangers—and greatly prospering, just like theory predicts.
... The majority of non-human animals have been selected to track photoperiod ("photoperiodic species") and exhibit seasonal changes in appearance, physiology and behavior in anticipation of seasons, in particular to prepare in advance for the energetic bottleneck of winter, characterized by increased thermoregulatory demands and decreased environmental caloric availability (Nelson et al., 2010;Prendergast et al., 2002). Although humans have been increasingly isolated in a microclimate with artificial heating and lighting diminishing the environmental influences of winter, they manifest seasonal changes in appetite, weight, and behavior resembling those of seasonal mammals, albeit to a lesser degree (Davis and Levitan, 2005;Wehr, 2001). However, a sizable proportion of humans manifest large seasonal changes resembling seasonal changes in photoperiodic mammals with increased appetite, sleepiness and sleep duration, as well as decreased level of energy, interest in sex and social activities, with fewer individuals meeting criteria for recurrent depressive episodes in fall/winter and full remission in spring and summer, commonly known as SAD (Davis and Levitan, 2005;Rosenthal et al., 1984). ...
... Although humans have been increasingly isolated in a microclimate with artificial heating and lighting diminishing the environmental influences of winter, they manifest seasonal changes in appetite, weight, and behavior resembling those of seasonal mammals, albeit to a lesser degree (Davis and Levitan, 2005;Wehr, 2001). However, a sizable proportion of humans manifest large seasonal changes resembling seasonal changes in photoperiodic mammals with increased appetite, sleepiness and sleep duration, as well as decreased level of energy, interest in sex and social activities, with fewer individuals meeting criteria for recurrent depressive episodes in fall/winter and full remission in spring and summer, commonly known as SAD (Davis and Levitan, 2005;Rosenthal et al., 1984). SAD, as now defined, was first characterized by a group including Thomas Wehr, Al Lewy, andNorman Rosenthal in 1984 (Rosenthal et al., 1984). ...
Overlapping pathways between mood and metabolic regulation have increasingly been reported. Although impaired regulation of adiponectin, a major metabolism-regulating hormone, has been implicated in major depressive disorder, its role in seasonal changes in mood and seasonal affective disorder-winter type (SAD), a disorder characterized by onset of mood impairment and metabolic dysregulation (e.g., carbohydrate craving and weight gain) in fall/winter and spontaneous alleviation in spring/summer, has not been previously studied. We studied a convenience sample of 636 Old Order Amish (mean (± SD), 53.6 (±14.8) years; 50.1% males), a population with self-imposed restriction on network electric light at home, and low prevalence of total SAD (t-SAD = syndromal + subsyndromal). We calculated the global seasonality score (GSS), estimated SAD and subsyndromal-SAD after obtaining Seasonal Pattern Assessment Questionnaires (SPAQs), and measured overnight fasting plasma adiponectin levels. We then tested associations between plasma adiponectin levels and GSS, t-SAD, winter-summer difference in self-reported sleep duration, and self-reported seasonal weight change, by using analysis of co-variance (ANCOVA) and linear regression analysis after adjusting for age, gender, and BMI. Participants with t-SAD (N = 14; 2.2%) had significantly lower plasma adiponectin levels (mean ± SEM, 8.76 ± 1.56 μg/mL) than those without t-SAD (mean ± SEM, 11.93 ± 0.22 μg/mL) (p = 0.035). In addition, there was significant negative association between adiponectin levels and winter-summer difference in self-reported sleep duration (p = 0.025) and between adiponectin levels and self-reported seasonal change in weight (p = 0.006). There was no significant association between GSS and adiponectin levels (p = 0.88). To our knowledge, this is the first study testing the association of SAD with adiponectin levels. Replication and extension of our findings longitudinally and, then, interventionally, may implicate low adiponectin as a novel target for therapeutic intervention in SAD.
... It has been suggested (at the ultimate level of explanation) that SAD is an adaptation to northern latitudes to conserve energy during historically predictable periods of dwindling food supply (Davis and Levitan, 2005;Eagles, 2004). However, we are not convinced that SAD is an adaptation to seasonal changes in food supply, nor to northern (or southern) latitudes. ...
... Increased need to sleep is typical for SAD. It has been suggested that it helps conserve energy when conserving energy yields greater organismal benefit than activity does (Davis and Levitan, 2005;Eagles, 2004). Increased need to sleep is a common sickness behaviour and it may also occur in other subtypes of depression in which an organism benefits from conserving energy (Anders et al., 2013). ...
Major depressive disorder constitutes one of the leading causes of disability worldwide. However, it is not a unitary disease — it is a heterogeneous syndrome, with patients differing remarkably in symptom profile, pathophysiology and treatment responsiveness. Previous attempts to subtype major depressive disorder have showed limited clinical applicability. We present a classification of major depressive disorder episodes based on the proximate mechanisms that led to the original mood change that caused the depressive episode. We identify discrete depression subtypes that are induced by: 1) infection, 2) long-term stress, 3) loneliness, 4) traumatic experience, 5) hierarchy conflict, 6) grief, 7) romantic rejection, 8) postpartum events, 9) the season, 10) chemicals, 11) somatic diseases and 12) starvation. We further examine the ultimate functions of these subtypes and show that not all types of mood changes that trigger depression are adaptive. Instead, some are clearly maladaptive and some are byproducts of other adaptations. In modern societies, low mood after adverse life events may turn into a pathological depressive state. Modern lifestyle increases susceptibility to inflammatory dysregulation and chronic stress, both of which increase the amount of proinflammatory cytokines in peripheral blood, leading to low mood and sickness behaviour. Proinflammatory cytokines may aggravate the previously adaptive short-term mood changes to a chronic maladaptive depressive state by preventing the normalization of mood after adverse life events. Subtyping depression enables an effective and intelligent long-term treatment of patients in each subtype by treating the underlying causes of depression.
... Most hypotheses include a concept of energy limitation, and an attempt to overcome a failure, defeat, danger, or shortage of resources. First, several related hypotheses suggest that depression may be a means to conserve energy during an adverse situation (Davis and Levitan, 2005;Eagles, 2004;Engel and Schmale, 1972;Thierry et al., 1984). This approach has been further refined to propose that depression is not merely for conservation, but for optimal energy reallocation. ...
... Fatigue, hypersomnia, psychomotor retardation, withdrawal, indecisiveness, increased appetite Davis and Levitan, 2005;Eagles, 2004;Engel and Schmale, 1972;Thierry et al., 1984 Signal social defeat (giving in) Symptoms help an individual accept lower social status, preventing futile dominance challenges, and signal this submission to more dominant individuals. ...
... It has been hypothesized that SAD is adaptive in highly seasonal environments, where increasing sleep during the winter would conserve energy and maintain thermoregulation, while increased energy and capacity for work would be beneficial during warmer, more productive months, coupled with potential advantages of SAD symptoms for pregnant women during the winter months [126,127]. It is easy to appreciate the adaptive value of such a trait prior to electrical lighting and in agrarian societies, and in areas with long, dark winters and food production concentrated in a subset of the year. ...
... It is easy to appreciate the adaptive value of such a trait prior to electrical lighting and in agrarian societies, and in areas with long, dark winters and food production concentrated in a subset of the year. If future research finds support for this hypothesis, SAD would be adaptive for a relatively small (and shrinking) percentage of the world that lives at high latitudes without access to modern lighting, and thus could be considered to be an evolutionary mismatch condition [126,127]. ...
Sleep is essential to cognitive function and health in humans, yet the ultimate reasons for sleep - i.e., why sleep evolved - remain mysterious. We integrate findings from human sleep studies, the ethnographic record, and the ecology and evolution of mammalian sleep to better understand sleep along the human lineage and in the modern world. Compared to other primates, sleep in great apes has undergone substantial evolutionary change, with all great apes building a sleeping platform or "nest." Further evolutionary change characterizes human sleep, with humans having the shortest sleep duration, yet the highest proportion of rapid eye movement (REM) sleep among primates. These changes likely reflect that our ancestors experienced fitness benefits from being active for a greater portion of the 24-hour cycle than other primates, potentially related to advantages arising from learning, socializing, and defending against predators and hostile conspecifics. Perspectives from evolutionary medicine have implications for understanding sleep disorders; we consider these perspectives in the context of insomnia, narcolepsy, seasonal affective disorder, circadian rhythm disorders, and sleep apnea. We also identify how human sleep today differs from sleep through most of human evolution, and the implications of these changes for global health and health disparities. More generally, our review highlights the importance of phylogenetic comparisons in understanding human health, including well-known links between sleep, cognitive performance and health in humans.
... Most hypotheses include a concept of energy limitation, and an attempt to overcome a failure, defeat, danger, or shortage of resources. First, several related hypotheses suggest that depression may be a means to conserve energy during an adverse situation (Davis and Levitan, 2005;Eagles, 2004;Engel and Schmale, 1972;Thierry et al., 1984). This approach has been further refined to propose that depression is not merely for conservation, but for optimal energy reallocation. ...
... Fatigue, hypersomnia, psychomotor retardation, withdrawal, indecisiveness, increased appetite Davis and Levitan, 2005;Eagles, 2004;Engel and Schmale, 1972;Thierry et al., 1984 Signal social defeat (giving in) Symptoms help an individual accept lower social status, preventing futile dominance challenges, and signal this submission to more dominant individuals. ...
Major depressive disorder (MDD) presents with a variety of symptoms and responds to a wide range of treatment interventions. Diagnostic criteria collapse multiple syndromes with distinct etiologies into the same disorder. MDD is typically understood as a malfunction of neurotransmission or brain circuitry regulating mood, pleasure and reward, or executive function. However, research from an evolutionary perspective suggests that the “normal” functioning of adaptations may also generate symptoms meeting diagnostic criteria. Functioning adaptations may be an underappreciated etiological pathway to MDD. Many adaptive functions for depressive symptoms have been suggested: biasing cognition to avoid losses, conserving energy, disengaging from unobtainable goals, signaling submission, soliciting resources, and promoting analytical thinking. We review the potential role of these adaptive functions and how they can lead to specific clusters of depressive symptoms. Understanding MDD from such a perspective reduces the heterogeneity of cases and may help to select the best intervention for each patient. We discuss the implications of different adaptive and maladaptive etiological pathways for the use of antidepressants and various modes of psychotherapy. In particular, instances of MDD caused by functioning adaptations may benefit most from treatments that support the adaptive function, or that target the precipitating causal stressor. We conclude that an evolutionary approach to the study of MDD may be one of the more promising approaches to reduce its heterogeneity and to better match patients and treatment.
... Some researchers have looked upon SAD from an evolutionary perspective. The onset of the vegetative symptoms (low energy, long sleep, weight gain) might naturally be related to photoperiod and the need for conservation of energy during certain seasons in order to favor reproduction and survival (53,54). While once an adaptive function, in contemporary modern life it rather presents as an unwanted temporary state of depression (54). ...
... The onset of the vegetative symptoms (low energy, long sleep, weight gain) might naturally be related to photoperiod and the need for conservation of energy during certain seasons in order to favor reproduction and survival (53,54). While once an adaptive function, in contemporary modern life it rather presents as an unwanted temporary state of depression (54). ...
... (5), p. 534]. Hysteria was also viewed entirely as a "woman's disease" whose cause was mostly impugned on the dominant Victorian morality of sexual prudery and constraint. 1 A century later, Hysteria, as a discrete psychiatric entity, was largely discredited, and begin to remit in the spring (10). Many individuals with SAD also experience pronounced food cravings and frequent incidents of binge eating during the winter months (11,12). ...
... It is not difficult to see how the dramatic social, economic, and environmental changes that occurred in the last few decades of the twentieth century have played a role in the emergence of modern "women's diseases" like BED and SAD. For instance, one of the most incompatible aspects of seasonality for the modern women is that increased appetite and food cravings are highly undesirable occurrences in societies that place a high value on an ultra-thin body ideal (10). These physiological changes are especially problematic and likely to contribute to substantial weight gain in the modern food environment with its superfluity of highly caloric and hyper-palatable foods. ...
Binge-eating disorder and seasonal affective disorder were first described as clinically relevant conditions in very close temporal proximity a few decades ago. Both disorders have a higher prevalence rate in woman than in men, are characterized by a high proneness-to-stress and manifest heightened responsiveness to high-calorie, hyper-palatable foods. In recent years, a compelling body of evidence suggests that foods high in sugar and fat have the potential to alter brain reward circuitry in a manner similar to that seen when addictive drugs like alcohol and heroin are consumed in excess. These findings have led to suggestions that some cases of compulsive overeating may be understood as an addiction to sweet, fatty, and salty foods. In this paper, it is proposed that high seasonality is a risk factor for binge eating, especially in those characterized by anxious and impulsive personality traits – associations that could only occur in an environment with a superfluity of, and easy access to, rich and tasty foods. Given the well-established links between binge eating and addiction disorders [Ref. (1–3) for reviews], it is also suggested that seasonality, together with the same high-risk psychological profile, exacerbates the likelihood of engaging in a broad range of addictive behaviors. Data from a community sample (n = 412) of adults tested these models using linear regression procedures. Results confirmed that symptoms of binge eating and other addictive behaviors were significantly inter-correlated, and that seasonality, gender, and addictive personality traits were strong statistical predictors of the variance in binge-eating scores. Seasonality and addictive personality traits also accounted for a significant proportion of the variance in the measure of addictive behaviors. Conclusions are discussed in the context of brain reward mechanisms, motivational alternations in response to chronic over-consumption, and their relevance for the treatment of excessive appetitive behaviors.
... These symptoms typically begin during autumn and end in spring and early summer. Although it has previously been suggested that SAD may have evolved as an adaptation to save energy during wintertime in northern latitudes during periods of food shortage (Davis and Levitan 2005), the evidence suggests that the most plausible explanation for winter depression ...
Major depressive disorder (MDD) is not a unitary disorder. From an evolutionary perspective, it should be divided into different subtypes based on triggering factors. Some of the symptoms of depression are adaptations to solve adaptive problems that trigger mood swings, while some others are maladaptive. MDD has become more common in societies that have adopted modern “Western” lifestyles. The evolutionary mismatch hypothesis suggests that this is because the human mind and body are not adapted to live under the characteristics of modern “Western” lifestyles. The evolutionary psychoneuroimmunological approach suggests that modern lifestyles increase the prevalence of systemic low-grade inflammation and chronic stress, which underlies neuroinflammation. Neuroinflammation triggers sickness behavior symptoms, many of which are the same as those observed in MDD, likely changing the previously adaptive mood into a maladaptive state of MDD.
... Similarly, negative psychological responses seem to function as a mechanism to steer clear of adverse bio-physical situations. For example, seasonal affective disorder (SAD), known as winter depression, is thought to have adaptive benefits, by reducing wasteful activity during the less productive winter seasons (Davis & Levitan, 2005;Sher, 2000). ...
A growing body of empirical evidence shows that experiences of nature provide people with diverse psychological benefits, including improved cognitive function and mental health. While our understanding of the proximate causes of these positive psychological responses of humans to nature has advanced, the ultimate (evolutionary) drivers behind them remain poorly understood.
In this study, we provide a summary of several widely accepted evolutionary hypotheses originating from Biophilia , reviewing their challenges and limitations. Subsequently, we propose a new evolutionary psychological hypothesis—the greenery hypothesis—that integrates recent findings in evolutionary psychiatry with many experimental results unexplained by existing hypotheses/theories.
Our proposed hypothesis states that humans have adapted to periodic severe drought and re‐watering cycles by developing both negative and positive psychological responses to the absence or presence of greenery within the landscape as cues to optimise their own behavioural activity.
The greenery hypothesis holds the potential to yield several insights into the fundamental understanding of human psychological responses to nature exposure with significant implications for various related fields, including psychiatry, urban planning, and biodiversity conservation and restoration.
Read the free Plain Language Summary for this article on the Journal blog.
... experienced by many people whose seasonal symptoms would not reach the clinical threshold for this disorder (Schlager et al., 1993;Harmatz et al., 2000;Avasthi et al., 2001;Demir et al., 2016;Arendt and Middleton, 2018). It has been suggested that the seasonal decrease in sexual function (and thus mating) may have evolutionary origins, such that births would be less likely to occur during the increasingly resource-poor autumn, and instead be biased toward early spring (Eagles, 2004;Davis and Levitan, 2005). In support, SAD is more common in people of reproductive age than those younger or older (Magnusson et al., 2000). ...
Seasonal affective disorder (SAD) involves a number of psychological and behavioral impairments that emerge during the low daytime light intensity associated with winter, but which remit during the high daytime light intensity associated with summer. One symptom frequently reported by SAD patients is reduced sexual interest and activity, but the endocrine and neural bases of this particular impairment during low daylight intensity is unknown. Using a diurnal laboratory rodent, the Nile grass rat (Arvicanthis niloticus), we determined how chronic housing under a 12:12 h day/night cycle involving dim low-intensity daylight (50 lux) or bright high-intensity daylight (1,000 lux) affects males’ copulatory behavior, reproductive organ weight, and circulating testosterone. We also examined the expression of mRNAs for the aromatase enzyme, estrogen receptor 1 (ESR1), and androgen receptor (AR) in the medial preoptic area (mPOA; brain site involved in the sensory and hormonal control of copulation), and mRNAs for the dopamine (DA) D1 and D2 receptors in both the mPOA and nucleus accumbens (NAC; brain site involved in stimulus salience and motivation to respond to reward). Compared to male grass rats housed in high-intensity daylight, males in low-intensity daylight displayed fewer mounts and intromissions when interacting with females, but the groups did not differ in their testes or seminal vesicle weights, or in their circulating levels of testosterone. Males in low-intensity daylight unexpectedly had higher ESR1, AR and D1 receptor mRNA in the mPOA, but did not differ from high-intensity daylight males in D1 or D2 mRNA expression in the NAC. Reminiscent of humans with SAD, dim winter-like daylight intensity impairs aspects of sexual behavior in a male diurnal rodent. This effect is not due to reduced circulating testosterone and is associated with upregulation of mPOA steroid and DA receptors that may help maintain some sexual motivation and behavior under winter-like lighting conditions.
... Se hará un enfoque en terapias que involucren manipulación de la luz porque, y aunque la información es fragmentaria, se sospecha que dentro de las causas últimas (evolucionistas) Este artículo fue publicado originalmente en el Blog de JFDO el 21-Nov-2018 y también está disponible en: https://www.juanferduque.com/ Aspectos Evolucionistas del Trastorno Afectivo Bipolar Página 4 de 7 hay una relación entre el TAB y la estacionalidad (Sherman, 2006(Sherman, , 2012, pues entre otras cosas no se debe dejar de lado una entidad como el desorden afectivo estacional (Davis & Levitan, 2005;Eagles, 2004;Sher, 2000) que prácticamente hace parte del gradiente bipolar. Y he aquí el meollo de este artículo. ...
El trastorno afectivo bipolar (TAB) es una condición que, dependiendo de su severidad, lleva al paciente del extremo de la euforia (o manía en casos clínicos) a la disforia (o depresión clínica) afecta a aproximadamente a aproximadamente al 4% de la población. Sobre el TAB hay considerable información sobre sus causas próximas y poca información sobre sus causas últimas (evolucionistas). Dentro de estos hay unos pocos autores que empiezan a señalar que el TAB podría tener, entre sus causas evolucionistas, un componente climático, dentro de la cual cabe resaltar que el TAB tiene una entidad muy emparentada llamada trastorno afectivo estacional. Teniendo en cuenta todo esto, se llama la atención sobre el hecho de que se necesita más investigación sobre las causas evolucionistas (últimas) de TAB que le den cohesión a la información fragmentaria que hay sobre las causas próximas del TAB, especialmente en lo que al efecto de la estacionalidad se refiere. Además de ser interesante desde el punto de vista científico, el que los facultativos, especialmente los psicólogos conozcan más sobre el TAB ayudará a tratar mejor a los pacientes.
... experienced by many people whose seasonal symptoms would not reach the clinical threshold for this disorder (Schlager et al., 1993;Harmatz et al., 2000;Avasthi et al., 2001;Demir et al., 2016;Arendt and Middleton, 2018). It has been suggested that the seasonal decrease in sexual function (and thus mating) may have evolutionary origins, such that births would be less likely to occur during the increasingly resource-poor autumn, and instead be biased toward early spring (Eagles, 2004;Davis and Levitan, 2005). In support, SAD is more common in people of reproductive age than those younger or older (Magnusson et al., 2000). ...
Light profoundly affects the behavior and physiology of almost all animals, including humans. One such effect in humans is that the level of illumination during the day positively contributes to affective well-being and cognitive function. However, the neural mechanisms underlying the effects of daytime light intensity on affect and cognition are poorly understood. One barrier for progress in this area is that almost all laboratory animal models studied are nocturnal. There are substantial differences in how light affects nocturnal and diurnal species, e.g., light induces sleep in nocturnal mammals and wakefulness in diurnal ones, like humans. Therefore, the mechanisms through which light modulates affect and cognition must differ between the chronotypes. To further understand the neural pathways mediating how ambient light modulates affect and cognition, our recent work has developed a diurnal rodent model, the Nile grass rat (Arvicanthis niloticus), by chronically manipulating daytime light intensity in grass rats housed under the same 12:12 hour light/dark cycle. This simulates lighting conditions during summer-like bright sunny days vs. winter-like dim cloudy days. Our work has revealed that chronic dim daylight intensity results in higher depression- and anxiety-like behaviors, as well as impaired spatial learning and memory. Furthermore, we have found that hypothalamic orexin is a mediator of these effects. A better understanding of how changes in daytime light intensity impinge upon the neural substrates involved in affect and cognition will lead to novel preventive and therapeutic strategies for seasonal affective disorder, as well as non-seasonal emotional or cognitive impairments associated with light deficiency.
... This difference, and the fact that appetitive symptoms are often the first to emerge during the short days of fall in patients with SAD, 6 suggests that increased eating plays a more fundamental role in the pathophysiology of SAD than it does in nonseasonal MDD. Indeed, several authors [22][23][24] have suggested that appetitive symptoms in SAD reflect an evolutionary adaptive mechanism to conserve energy in the face of harsh environmental conditions. Genetic data further support the concept of a "seasonal thrifty phenotype. ...
Objective:
We previously reported that morning bright light therapy is efficacious in adults with nonseasonal major depressive disorder (MDD), both on its own and in combination with fluoxetine. Given that appetitive symptoms predict response to bright light therapy in seasonal depression, we examined, in this secondary analysis, whether the same held true in these nonseasonal MDD patients.
Methods:
Data were collected from October 7, 2009, to March 11, 2014. One hundred twenty-two patients who met DSM-IV-TR criteria for MDD without a seasonal pattern were randomly assigned to light monotherapy, fluoxetine, combination light and fluoxetine, or double-placebo (inactivated negative ion generator plus placebo pill). Multiple regression assessed the percentage change in Montgomery-Asberg Depression Rating Scale (MADRS) scores based on treatment condition, appetitive symptom score at baseline (sum of 4 items on the Structured Interview Guide for the Hamilton Depression Rating Scale, Seasonal Affective Disorders version), and the condition-by-appetitive score interaction. Sex was considered as a possible moderator of these effects.
Results:
The overall regression model predicting treatment response was highly significant (P < .001), and the treatment condition-by-appetitive score interaction was a strong predictor of MADRS change scores (t = 2.65, P = .009). For individuals in the placebo group, more appetitive symptoms at baseline predicted less decrease in MADRS scores at 8 weeks (r = -0.37; large effect size). In contrast, for individuals in the active treatment groups, more appetitive symptoms at baseline predicted more of a decrease in depression scores at 8 weeks (fluoxetine group r = +0.23, medium effect size; light therapy group r = +0.11, small effect size; combination group r = +0.32, medium to large effect size). No moderation effect of sex was found.
Conclusions:
More severe appetitive symptoms at baseline predicted treatment response differentially across the 4 treatment groups. Contrary to prior findings in seasonal depression, this association was not robust for MDD patients receiving light therapy alone, although it was stronger in patients receiving fluoxetine with or without light. As the group sample sizes were modest, the current findings should be considered as preliminary only.
Trial registration:
ClinicalTrials.gov identifier: NCT00958204.
... The role of temperature in life history strategies is probably similarly complicated. Temperature is related to environmental resources and higher temperature is itself an environmental resource (Davis & Levitan 2005;IJzerman et al. 2015a). Moreover, temperature has also been hypothesized in various ways to be implicated in increased encephalization (Naya et al. 2016), a development that seems crucial in flexible predictive control. ...
A total of 80 authors working in a variety of scientific disciplines commented on the theoretical model of CLimate, Aggression, and Self-control in Humans (CLASH). The commentaries cover a wide range of issues, including the logic and assumptions of CLASH, the evidence in support of CLASH, and other possible causes of aggression and violence (e.g., wealth, income inequality, political circumstances, historic circumstances, pathogen stress). Some commentaries also provide data relevant to CLASH. Here we clarify the logic and assumptions of CLASH and discusses its extensions and boundary conditions. We also offer suggestions for future research. Regardless of whether none, some, or all of CLASH is found to be true, we hope it will stimulate future research on the link between climate and human behavior. Climate is one of the most presing issues of our time.
... The role of temperature in life history strategies is probably similarly complicated. Temperature is related to environmental resources and higher temperature is itself an environmental resource (Davis & Levitan 2005;IJzerman et al. 2015a). Moreover, temperature has also been hypothesized in various ways to be implicated in increased encephalization (Naya et al. 2016), a development that seems crucial in flexible predictive control. ...
Planning for the future may encourage apparently “impulsive” behaviour when the future is anticipated to be bleak. Thus, a seeming failure of self-control in reactive violence could be caused not by a disinclination to plan ahead, but by virtue of this ability. Furthermore, we point to empirical and theoretical shortcomings in the authors' case, such as a failure to distinguish proximate and ultimate explanations.
... The role of temperature in life history strategies is probably similarly complicated. Temperature is related to environmental resources and higher temperature is itself an environmental resource (Davis & Levitan 2005;IJzerman et al. 2015a). Moreover, temperature has also been hypothesized in various ways to be implicated in increased encephalization (Naya et al. 2016), a development that seems crucial in flexible predictive control. ...
We comment on the proposition “that lower temperatures and especially greater seasonal variation in temperature call for individuals and societies to adopt … a greater degree of self-control” (Van Lange et al., sect. 3, para. 4) for which we cannot find empirical support in a large data set with data-driven analyses. After providing greater nuance in our theoretical review, we suggest that Van Lange et al. revisit their model with an eye toward the social determinants of self-control.
... The role of temperature in life history strategies is probably similarly complicated. Temperature is related to environmental resources and higher temperature is itself an environmental resource (Davis & Levitan 2005;IJzerman et al. 2015a). Moreover, temperature has also been hypothesized in various ways to be implicated in increased encephalization (Naya et al. 2016), a development that seems crucial in flexible predictive control. ...
Contrary to one assumption of CLASH, we suggest that colder rather than warm climates are the harsh, unpredictable ones, thus requiring greater self-control. We propose shifting emphasis from predictability to utility of prediction. Northern climates may be less predictable than tropical ones, making predictions and planning far more important, insofar as they can prevent fatalities and promote other pragmatic benefits.
... The role of temperature in life history strategies is probably similarly complicated. Temperature is related to environmental resources and higher temperature is itself an environmental resource (Davis & Levitan 2005;IJzerman et al. 2015a). Moreover, temperature has also been hypothesized in various ways to be implicated in increased encephalization (Naya et al. 2016), a development that seems crucial in flexible predictive control. ...
The CLASH model is not convincing for two reasons. First, it ignores prior research proposing very similar ideas in a more compelling fashion. Second, it dismisses the role of genetic factors in shaping criminal propensities across population groups, opting for a facultative view of life history evolution that does not seem to square with current
evidence.
... The role of temperature in life history strategies is probably similarly complicated. Temperature is related to environmental resources and higher temperature is itself an environmental resource (Davis & Levitan 2005;IJzerman et al. 2015a). Moreover, temperature has also been hypothesized in various ways to be implicated in increased encephalization (Naya et al. 2016), a development that seems crucial in flexible predictive control. ...
The CLimate, Aggression, and Self-control in Humans (CLASH) proposes that aggression and violence increase as climates become hotter and seasonal variation becomes smaller by influencing time-orientation and self-control. Emerging empirical evidence supporting the model is reviewed. Wealth, income inequality, and pathogen stress as powerful influences of these processes are also discussed. We conclude by discussing the theoretical and societal importance of climate change in shaping violence.
... The role of temperature in life history strategies is probably similarly complicated. Temperature is related to environmental resources and higher temperature is itself an environmental resource (Davis & Levitan 2005;IJzerman et al. 2015a). Moreover, temperature has also been hypothesized in various ways to be implicated in increased encephalization (Naya et al. 2016), a development that seems crucial in flexible predictive control. ...
We comment on the proposition “that lower temperatures and especially greater seasonal variation in temperature calls for individuals and societies to adopt…a greater degree of self-control”, for which we cannot find empirical support in a large dataset with data-driven analyses. After providing more nuance in our theoretical review, we suggest revisiting their model with an eye to the social determinants of self-control.
... Generally, seasonality is regarded as an evolutionary adaptive mechanism of adjustment to a changing environment [7]. There is a vast literature on animals detailing seasonal fluctuations in a wide variety of variables (e.g., [1,9,11,28,41,52]). ...
Circannual rhythms and seasonality have long been in the interest of research. In humans, seasonal changes in mood have been extensively investigated since a substantial part of the population experiences worsening of mood during winter. Questions remain regarding accompanying physiological phenomena. We report seasonal effects on the acoustic startle response in a cross-sectional (n = 124) and a longitudinal sample (n = 23). Startle magnitudes were larger in winter (sample 1: p = 0.026; sample 2: p = 0.010) compared to summer months. Although the findings need to be replicated they may have implications regarding the timing of startle experiments.
... The role of temperature in life history strategies is probably similarly complicated. Temperature is related to environmental resources and higher temperature is itself an environmental resource (Davis & Levitan 2005;IJzerman et al. 2015a). Moreover, temperature has also been hypothesized in various ways to be implicated in increased encephalization (Naya et al. 2016), a development that seems crucial in flexible predictive control. ...
Considering purely climate, Southern countries are less harsh and more predictable than Northern countries. From a historical perspective, freezing winters resulting in less available resources contribute to the development of strong future orientation (FO). The paradox is that FO contributes to accumulation of resources in the long run, making individuals’ immediate living conditions less harsh, leading to slower life strategies.
... The role of temperature in life history strategies is probably similarly complicated. Temperature is related to environmental resources and higher temperature is itself an environmental resource (Davis & Levitan 2005;IJzerman et al. 2015a). Moreover, temperature has also been hypothesized in various ways to be implicated in increased encephalization (Naya et al. 2016), a development that seems crucial in flexible predictive control. ...
Planning for the future may encourage apparently ‘impulsive’ behaviour when the future is anticipated to be bleak. Thus, a seeming failure of self-control in reactive violence could be caused not by a disinclination to plan ahead, but by virtue of this ability. Furthermore, we point to empirical and theoretical shortcomings in the authors’ case, such as a failure to distinguish proximate and ultimate explanations.
... The role of temperature in life history strategies is probably similarly complicated. Temperature is related to environmental resources and higher temperature is itself an environmental resource (Davis & Levitan 2005;IJzerman et al. 2015a). Moreover, temperature has also been hypothesized in various ways to be implicated in increased encephalization (Naya et al. 2016), a development that seems crucial in flexible predictive control. ...
Worldwide there are substantial differences within and between countries in aggression and violence. Although there are various exceptions, a general rule is that aggression and violence increase as one moves closer to the equator, which suggests the important role of climate differences. While this pattern is robust, theoretical explanations for these large differences in aggression and violence within countries and around the world are lacking. Most extant explanations focus on the influence of average temperature as a factor that triggers aggression (The General Aggression Model), or the notion that warm temperature allows for more social interaction situations (Routine Activity Theory) in which aggression is likely to unfold. We propose a new model of CLimate, Aggression, and Self-control in Humans (CLASH) that seeks to understand differences within and between countries in aggression and violence in terms of differences in climate. Lower temperatures, and especially larger degrees of seasonal variation in climate, calls for individuals and groups to adopt a slower life history strategy, and exert more focus on the future (versus present), and a stronger focus on self-control. The CLASH model further outlines that slow life strategy, future orientation, and strong self-control are important determinants of inhibiting aggression and violence. We also discuss how CLASH is different from other recently developed models that emphasize climate differences for understanding conflict. We conclude by discussing the theoretical and societal importance of climate in shaping individual and societal differences in aggression and violence.
... The expression (or not) of such rhythms depend on the photoperiod and its fluctuation across seasons (Gwinner, 2003). Humans are also sensitive to photoperiod changes because afflictions such as seasonal affective disorder can be diagnosed at the arrival of autumn and winter (Davis & Levitan, 2005). In invertebrates, insects are striking examples of organisms displaying a photoperiodic response. ...
This thesis aims to discriminate between embryos development towards either sexual or asexual reproduction types in pea aphids, Acyrthosiphon pisum, at the genomic level. This discrimination involves the creation of a post-transcriptional regulation network between microRNAs and mRNAs whose kinetic expressions change depending on the embryogenesis. It also involves a study of this network's interaction modules using formal concept analysis. To do so, a three-step strategy was set up. First the creation of an interaction network between the pea aphid's microRNAs and mRNAs. The network is then reduced by keeping only microRNAs and mRNAs which possess differential kinetics between the two embryogeneses, these are obtained using high-throughput sequencing data. Finally the remaining network is analysed using formal concept analysis. Analysing the network allowed for the identification of several functions of potential interest such as oogenesis, transcriptional regulation or even neuroendocrine system. In addition to network analysis, formal concept analysis was used to create a new method to repair a bipartite graph based on its topology and a method to visualise a bipartite graph using its formal concepts.
... On the other hand, the hypothalamic DA neurons may also be involved in modulating the nonreproductive traits, e.g. the behavioral and affective adaptation and/or maladaptation associated with altered ambient lighting conditions [8]. Although entering an energy conserving state during the winter could constitute an adaptive evolutionary mechanism that aided the survival for our ancestors, the recurrent winter depression in SAD is undoubtedly a maladaptation in the modern era [6,10]. ...
Light has profound effects on mood regulation as exemplified in Seasonal Affective Disorder (SAD) and the therapeutic benefits of light therapy. However, the underlying neural pathways through which light regulates mood are not well understood. Our previous work has developed the diurnal grass rat, Arvicanthis niloticus, as an animal model of SAD. Following housing conditions of either 12:12hr Dim Light:Dark (DLD) or 8:16hr Short Photoperiod (SP), which mimic the lower light intensity or short day-length of winter, respectively, grass rats exhibit an increase in depression-like behavior compared to those housed in a 12:12hr Bright Light:Dark (BLD) condition. Furthermore, we revealed that the orexinergic system is involved in mediating the effects of light on mood and anxiety. To explore other potential neural substrates involved in the depressive phenotype, the present study examined hypothalamic dopaminergic (DA) and somatostatin (SST) neurons in the brains of grass rats housed in DLD, SP and BLD. Using immunostaining for tyrosine hydroxylase (TH) and SST, we found that the number of TH- and SST-ir cells in the hypothalamus was significantly lower in the DLD and SP groups compared to the BLD group. We also found that treating BLD animals with a selective orexin receptor 1 (OX1R) antagonist SB-334867 significantly reduced the number of hypothalamic TH-ir cells. The present study suggests that the hypothalamic DA neurons are sensitive to daytime light deficiency and are regulated by an orexinergic pathway. The results support the hypothesis that the orexinergic pathways mediate the effects of light on other neuronal systems that collectively contribute to light-dependent changes in the affective state.
Copyright © 2015. Published by Elsevier Ireland Ltd.
... These observations lead to a long-debated hypothesis on the adaptive role of depression [56], including SAD [57], and suggest that MDD variants are subject to selective regimes different from other psychiatric disease. As mentioned above, SAD is the best example of a mood disorder directly triggered by photoperiod changes. ...
Background
The temporal coordination of biological processes into daily cycles is a common feature of most living organisms. In humans, disruption of circadian rhythms is commonly observed in psychiatric diseases, including schizophrenia, bipolar disorder, depression and autism. Light therapy is the most effective treatment for seasonal affective disorder and circadian-related treatments sustain antidepressant response in bipolar disorder patients. Day/night cycles represent a major circadian synchronizing signal and vary widely with latitude.ResultsWe apply a geographically explicit model to show that out-of-Africa migration, which led humans to occupy a wide latitudinal area, affected the evolutionary history of circadian regulatory genes. The SNPs we identify using this model display consistent signals of natural selection using tests based on population genetic differentiation and haplotype homozygosity. Signals of natural selection driven by annual photoperiod variation are detected for schizophrenia, bipolar disorder, and restless leg syndrome risk variants, in line with the circadian component of these conditions.Conclusions
Our results suggest that human populations adapted to life at different latitudes by tuning their circadian clock systems. This process also involves risk variants for neuropsychiatric conditions, suggesting possible genetic modulators for chronotherapies and candidates for interaction analysis with photoperiod-related environmental variables, such as season of birth, country of residence, shift-work or lifestyle habits.
... It is also more common in women during reproductive age. It has been hypothesized that seasonal changes in food intake, libido, and behavior are advantageous, as they would increase reproductive success in women by favoring weight gain in the fall, with weight gain coinciding with the second trimester of pregnancy, when most of the gain has to take place (58). Furthermore, the decreased libido experienced by women during the winter months would discourage intercourse and thus decrease the chances of birth with the following winter approaching, the least conducive time of the year to the survival of neonates. ...
Sleep duration has progressively fallen over the last 100 years while obesity has increased in the past 30 years. Several studies have reported an association between chronic sleep deprivation and long-term weight gain. Increased energy intake due to sleep loss has been listed as the main mechanism. The consequences of chronic sleep deprivation on energy expenditure have not been fully explored. Sleep, body weight, mood and behavior are subjected to circannual changes. However, in our modern environment seasonal changes in light and ambient temperature are attenuated. Seasonality, defined as cyclic changes in mood and behavior, is a stable personality trait with a strong genetic component. We hypothesize that the attenuation in seasonal changes in the environment may produce negative consequences, especially in individuals more predisposed to seasonality, such as women. Seasonal affective disorder, a condition more common in women and characterized by depressed mood, hypersomnia, weight gain, and carbohydrate craving during the winter, represents an extreme example of seasonality. One of the postulated functions of sleep is energy preservation. Hibernation, a phenomenon characterized by decreased energy expenditure and changes in the state of arousal, may offer useful insight into the mechanisms behind energy preservation during sleep. The goals of this article are to: a) consider the contribution of changes in energy expenditure to the weight gain due to sleep loss; b) review the phenomena of seasonality, hibernation, and their neuroendocrine mechanisms as they relate to sleep, energy expenditure, and body weight regulation.
... Human responses to seasonal changes in the natural photoperiod were more robust prior to the Industrial Revolution and have since been increasingly suppressed by man-made alterations in the environment (4,8). Seasonal changes in mood, with seasonal affective disorder being on the extreme end of the spectrum, have been theorized to have evolved to facilitate weight gain and the conservation of energy to endure winter food shortages and cold temperatures (9). Seasonal affective disorder typically begins in the fall when light exposure dwindles and is characterized by increased appetite, carbohydrate cravings, hypersomnia, lethargy, psychomotor retardation, and anhedonia. ...
In this issue of the American Journal of Epidemiology, McFadden et al. (Am J Epidemiol. 2014;180(3):245–250) report findings on the relationship between light exposure at night and obesity from a cross-sectional study of United Kingdom
women. Their research extends findings from a previous study with elderly participants by including a larger sample size of
over 100,000 women and a broader age range of 16 years or older. The findings are consistent with animal studies showing that
prolonged light exposure leads to weight gain. Humans’ circadian, circannual, and metabolic regulatory systems evolved to
be adaptive in environments that were quite different from those faced in modern industrial society. Technology has allowed
exposures to levels and timing of light, nutrient intake, and physical activity never before possible. This commentary discusses
how nighttime light exposure can increase the risk of obesity and the metabolic syndrome by disrupting circadian and circannual
rhythms.
... The expression (or not) of such rhythms depend on the photoperiod and its fluctuation across seasons (Gwinner, 2003). Humans are also sensitive to photoperiod changes because afflictions such as seasonal affective disorder can be diagnosed at the arrival of autumn and winter (Davis & Levitan, 2005 ). In invertebrates , insects are striking examples of organisms displaying a photoperiodic response. ...
Aphids are major crop pests and show a high level of phenotypic plasticity. They display a seasonal, photoperiodically-controlled polyphenism during their life cycle. In spring and summer, they reproduce efficiently by parthenogenesis. At the end of summer, parthenogenetic individuals detect the transition from short nights to long nights, which initiates the production of males and oviparous females within their offspring. These are the morphs associated with the autumn season. Deciphering the physiological and molecular events associated with this switch in reproductive mode in response to photoperiodic conditions is thus of key interest for understanding and explaining the remarkable capacity of aphids to adapt to fluctuations in their environment. The present review aims to compile earlier physiological studies, focussing on the neuroendocrine control of seasonal photoperiodism, as well as a series of large-scale transcriptomic approaches made possible by the recent development of genomic resources for the model aphid species: the pea aphid Acyrthosiphon pisum. These analyses identify genetic programmes putatively involved in the control of the initial steps of detection and transduction of the photoperiodic signal, as well as in the regulation of the switch between asexual and sexual oogenesis within embryonic ovaries. The contribution of small RNAs pathways (and especially microRNAs) in the post-transcriptional control of gene expression, as well as the role of epigenetic mechanisms in the regulation of genome expression associated with the photoperiodic response, is also summarized.
... Over the past few decades, a number of chronobiological studies have explored the effects of season of birth on several developmental traits and susceptibility to illnesses, including obesity (Wattie et al., 2008) and major psychiatric disorders (Boyd et al., 1986;Moore et al., 2001;Torrey & Miller, 1997). To date, there is solid evidence for an effect of season of birth on the risk of schizophrenia and bipolar disorder (Davies et al., 2003), with an excess of birth in winter/spring months for those individuals diagnosed with major affective disorder; moreover, some preliminary evidence of birth seasonality has been shown for patients with seasonal affective disorder and their unaffected siblings (Pjrek et al., 2007), consistent with the hypothesis that high degree of seasonality, once adaptive trait promoting better reproductive potential in our ancestors, is now associated with maladaptive behaviors-such as craving for calorie dense foods-predisposing to seasonal weight gain (Davis & Levitan, 2005). ...
Cardiovascular risk factors, such as abdominal obesity and obesity in general, are very prevalent among patients with bipolar disorder (BD). Although long-term use of psychotropic medications is an important determinant of these risk factors, other evidence suggests that early development may interact with the mood disorder diathesis to exponentially increase the risk of obesity. The goal of our study was to test whether season of birth is associated with adult body mass index (BMI) and abdominal obesity in individuals with bipolar disorder. We compared season of birth effects on BMI in 375 adult patients with bipolar disorder and 196 adult patients with unipolar major depression. We found a significant season of birth effect on BMI in patients with bipolar disorder, but not unipolar. In patients with bipolar disorder, season of birth was also associated with waist circumference, with a stronger effect in males. Season of birth affects adult BMI and waist circumference in patients with bipolar disorder, but not in patients with unipolar depression. Our results suggest that early environmental factors, yet to be identified, interact with specific neurobiological features of bipolar disorder to determine stable traits and disease risk factors in adult life. (Author correspondence: sorecai@upmc.edu ).
... The expression (or not) of such rhythms depend on the photoperiod and its fluctuation across seasons (Gwinner, 2003). Humans are also sensitive to photoperiod changes because afflictions such as seasonal affective disorder can be diagnosed at the arrival of autumn and winter (Davis & Levitan, 2005). In invertebrates, insects are striking examples of organisms displaying a photoperiodic response. ...
Aphids are among the rare organisms that can change their reproductive mode across their life cycle. During spring and summer they reproduce clonally and efficiently by parthenogenesis. At the end of summer aphids perceive the shortening of day length which triggers the production of sexual individuals - males and oviparous females - that will mate and lay overwintering cold-resistant eggs. Recent large scale transcriptomic studies allowed the discovery of transcripts and functions such as nervous and hormonal signaling involved in the early steps of detection and transduction of the photoperiodic signal. Nevertheless these experiments were performed under controlled conditions when the photoperiod was the only varying parameter. To characterize the response of aphids under natural conditions, aphids were reared outdoor both in summer and autumn and material was collected to compare their transcriptomic profile using a cDNA microarray containing around 7000 transcripts. Statistical analyses revealed that close to 5% of these transcripts (367) were differentially expressed at two developmental stages of the process in response to the autumnal environmental conditions. Functional classification of regulated transcripts confirmed the putative contribution of the neuro-endocrine system in the process. Furthermore, these experiments revealed the regulation of transcripts involved in juvenile hormone synthesis and signaling pathway, confirming the key role played by these molecules in the reproductive mode switch. Aphids placed under outdoor conditions were confronted to a range of abiotic factors such as temperature fluctuations which was confirmed by the differential expression of an important proportion of heat shock protein transcripts between the two seasons. Finally, this original approach completed the understanding of genetic programs involved in aphid phenotypic plasticity.
... It has thus been suggested that fall/ winter increases in eating behavior, weight, and sleep might reflect the vestigial human expression of a basic evolutionary process, present across multiple species, ensuring maximum conservation of energy when food supplies are becoming scarce (Rosenthal et al., 1987b; Sher, 2000; see also Thomson, 1950). Until recent time, by conserving energy during seasonal famines, such a process might have conferred both individual survival (Rosenthal et al., 1987b) and/or a reproductive advantage (Eagles, 2004; Davis and Levitan, 2005) in women of childbearing years. SAD sufferers are mostly women of 286 K.V. DANILENKO AND R.D. LEVITAN childbearing age, and estrogens may thus play a role in this regard. ...
Seasonal variation in photoperiod may affect psychosocial and physical well‐being in healthy persons. We tested this hypothesis in healthy pre‐menopausal women, without a history of mood disorders, living year‐round in Reykjavik, Iceland (64.1°N). Participants reported daily self‐assessments of well‐being throughout a complete ovulatory menstrual cycle in summer and/or winter (70% participated in both seasons). Scores for mood, cognitive acuity, social support, physical health and a composite of these four indicators were each significantly higher in summer than in winter (linear mixed effects models: p < .001 for each model); tiredness did not differ by season. The effect of season was not significantly changed by inclusion of body mass index and/or age as covariates. Some prior studies have been hampered by sparse time sampling, inattention to covariates and/or relying on recalled data. This is to our knowledge the first investigation to test the study hypothesis with daily real‐time data spanning complete ovulatory menstrual cycles in each of two seasons. This dense sampling has revealed modest seasonal variation in well‐being in healthy women. Daylength (sunlight exposure) is likely a major, but not necessarily sole, factor in these seasonal differences in well‐being; temperature is likely less important given Iceland's relatively moderate (for its high latitude) seasonal temperature swings.
Seasonal variations have long been observed in various aspects of human life. While there is an abundance of research that has characterized seasonality effects in, for example, cognition, mood, and behavior, including studies of underlying biophysical mechanisms, direct measurements of seasonal variations of brain functional activities have not gained wide attention. We have quantified seasonal effects on functional connectivity as derived from MRI scans. A cohort of healthy human subjects was divided into four groups based on the seasons of their scanning dates as documented in the image database of the Human Connectome Project. Sinusoidal functions were used as regressors to determine whether there were significant seasonal variations in measures of brain activities. We began with the analysis of seasonal variations of the fractional amplitudes of low frequency fluctuations of regional functional signals, followed by the seasonal variations of functional connectivity in both global- and network-level. Furthermore, relevant environmental factors, including average temperature and daylength, were found to be significantly associated with brain functional activities, which may explain how the observed seasonal fluctuations arise. Finally, topological properties of the brain functional network also showed significant variations across seasons. All the observations accumulated revealed seasonality effects of human brain activities in a resting-state, which may have important practical implications for neuroimaging research.
Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of the term varies according to local climate, cultures, and customs. When it is spring in the Northern Hemisphere, it is autumn in the Southern Hemisphere and vice versa. At the spring (or vernal) equinox, days and nights are approximately twelve hours long, with daytime length increasing and nighttime length decreasing as the season progresses until the Summer Solstice in June (Northern Hemisphere) and December (Southern Hemisphere).
In this research, the Biblical verses dealing with the spring are described. Therefore, the research presents the characteristics of the spring, and the health effects on the humans. Thus, the health effects related to the physical activity, ophthalmological, gastroenterological, cardiovascular, cerebrovascular, lipid lowering, neurological, endocrinological, dermatological, sensorineural hearing loss, hematological, urological, hemodialysis patients, respiratory conditions, allergy, autoimmune diseases, metabolic disease: gout, orthopedics, urological, pediatrics, seasonality of birth, fertilization rates, obstetrical complications, infectious diseases, poisonings, oncological, and mental disorders are presented.
In the recent years, the diagnostic possibilities have been validated through scientific research and have shown medicinal value in the diagnostics and the management of conditions associated with the spring.
This research has shown that the awareness of the spring has accompanied human during the long years of our existence.
Tryptophan is the essential amino acid precursor to the monoamine neurotransmitter serotonin, which is associated with several brain functions such as modulating mood, cognition, vomiting, impulsivity as well as sleep and circadian rhythm. The latter is due to serotonin's role as a precursor for melatonin—a light-sensitive hormone underlying the complex sleep–wake cycles in vertebrates. Melatonin and tryptophan supplementation have proven useful treatments in certain contexts, including depression, traumatic brain injury, delayed sleep phase syndrome, delirium, childhood parasomnias and insomnia. Background information and physiology of these two biomolecules are provided followed by investigation of the evidence for their clinical significance.
En el artículo reseñado aquí se propone que la hipomanía evolucionó como un mecanismo de defensa para anular la depresión, estado que habría sido mortal para nuestros antepasados en el pleistoceno. De pronto sucedió así: la inteligencia de Homo sapiens amplificó las emociones, surgiendo la depresión y ansiedad. Para contrarrestar la inhibición depresiva, la hipomanía evolucionó. El artículo es interesante, y aunque reconoce que es un mecanismo de defensa “en el límite de llegar a perder de llegar a perder el control", minimiza los riesgos de una hipomanía. La perspectiva del artículo reseñado aquí y el par de consejos que doy al final, son adecuados para Trastornos Bipolares leves o TAB II. Para TAB I se recomienda otro abordaje.
Objectives: Maternal-foetal tryptophan metabolism plays multiple roles in neurodevelopment and immunomodulation across pregnancy. Tryptophan and the immune system are both influenced by the seasons of the year. We thus compared tryptophan and kynurenine levels in subgroups of pregnant women defined by maternal seasonality and season-of-conception (SoC).
Methods: Maternal plasma samples taken at 9–15 and 23–29 weeks of pregnancy were analysed in 47 women with full or sub-syndromal Seasonal Affective Disorder (SAD) and 144 pregnant controls. Repeated measure ANCOVAs compared tryptophan and kynurenine levels in the two study groups over the two pregnancy sampling times, using SoC as a moderator.
Results: Significant differences in both plasma tryptophan and kynurenine were found across the eight subgroups defined by maternal seasonality and SoC. These results were independent of the state of depression.
Conclusions: Pregnant women with a history of full or sub-syndromal SAD exhibited a different pattern of plasma tryptophan and kynurenine across the seasons compared to control mothers, independent of current mood state. Follow-up of the children will determine the implications of these findings for neurodevelopment and psychiatric risk. Maternal seasonality and SoC may be important considerations when studying tryptophan and its metabolites in human pregnancy and foetal brain development.
Apparently inconsistent with the CLASH model, animal research relates predictable environments to rigid routine behaviors and aggression. However, our work on evolutionary and neural adaptations to (un)predictable environments may be able to reconcile the CLASH model with the animal research, but also suggests complexities beyond the dichotomous approach of CLASH.
There is an expanding interest in the evolutionary aspects of psychiatric illnesses including affective disorders in an effort to understand why these conditions, which carry a disadvantage in terms of reproduction and adaptation, or why their frequency does not show a decrease from generation to generation and how these conditions do not tend gradually to disappear. Each of the affective phases has several advantageous characteristics enhancing fitness and adaptation as do affective disorders as well. However, mood disorders are complex and multifaceted which have a polygenic and multifactorial background; therefore decomposing them into more atomic characteristics aids the separation and better understanding of their adaptive aspects. Approaching affective illness from the aspect of affective temperaments helps this decomposition and also the understanding of how pathological symptoms may have their roots in adaptation to environmental and also social challenges. Such a perspective on affective disorders helps not only their better understanding, but also promises a differential approach to prevention, screening, diagnosis and treatment, as well as reducing the stigma associated with these mental illnesses.
We propose that depression can be viewed as an adaptation to conserve energy after the perceived loss of an investment in a vital resource such as a relationship, group identity, or personal asset. Tendencies to process information negatively and experience strong biological reactions to stress (resulting from genes, trauma, or both) can lead to depressogenic beliefs about the self, world, and future. These tendencies are mediated by alterations in brain areas/networks involved in cognition and emotion regulation. Depressogenic beliefs predispose individuals to make cognitive appraisals that amplify perceptions of loss, typically in response to stressors that impact available resources. Clinical features of severe depression (e.g., anhedonia, anergia) result from these appraisals and biological reactions that they trigger (e.g., autonomic, immune, neurochemical). These symptoms were presumably adaptive in our evolutionary history, but are maladaptive in contemporary times. Thus, severe depression can be considered an anachronistic manifestation of an evolutionarily based “program.”
Seasonal affective disorder (or winter depression) is a frequent disorder, recurring during winter and often underdiagnosed. One of the first hypotheses was the phase shift hypothesis (phase delay). Recently, genetics, retinal sensitivity and its links with melanopsin, serotonin and dopamine illustrate the complexity of seasonal mood regulation. Bright light therapy is widely accepted as first-line treatment. Now, the central challenge is the prevention of depression recurrence each fall/winter season. The therapeutic alliance quality is crucial for compliance and long-term efficiency.
The thrifty genotype and phenotype hypotheses were developed to explain the rapid increase in diabetes and obesity in developed countries around the world. Most subsequent "thrifty" research has focused on the early developmental origins of the metabolic syndrome and cardio-metabolic disease. The goal of this manuscript is to review an emerging line of research that uses a similar thrifty framework to understand the early developmental origins of eating-related phenotypes that have primary relevance to many psychiatric disorders. Given the important role of environmental adversity in various psychiatric disorders that involve overeating, and their early age of onset, it is likely that several thrifty mechanisms are relevant in this regard. Understanding the early origins of increased eating behaviour based on a thrifty model might point the way to highly targeted preventative interventions during critical periods of development, and provide a new way of addressing these common and difficult to treat disorders.
In recent years, there has been considerable improvement in the diagnostic criteria and epidemiology of seasonal affective disorder (SAD). This condition is a cyclically recurring mood and neuro-vegetative disorder that particularly affects populations residing in northern latitudes. It is characterised by regular depressive episodes in the autumn and winter, and non-depressive periods in the spring and summer. To date, the aetiology of SAD has not been identified. The leading hypotheses include seasonal variation of the photoperiod, circadian phase shift and neurotransmitter dysfunction. A number of recent studies suggest that physical exercise may provide an effective and easily accessible treatment for patients suffering from SAD. Despite growing research efforts, the palliative effects of exercise on depression and seasonal mood disorders are not clearly understood. This review assesses the clinical and physiological evidence which suggests that exercise intervention may facilitate effective treatment for SAD. Particular emphasis is given to circadian mechanisms that have been hypothesised to explain mood-enhancing affects of physical exercise.
Summary Objective Depressive Disorders are complex disorders: psychological, neurobiological, genetic, social, cultural and also chronobiological factors contribute to the pathogenesis. In the scientific literature it has been commonly reported that modifications of circadian rhythms are frequent in patients with Depressive Disorders during symptomatic phas- es. However, there are no data concerning circadian patterns before the beginning of the mood disorder. The present study investigates the patterns of pre-morbid sleep and the general activity circadian profile, which characterizes patients affected by a De- pressive Disorder compared with healthy individuals. Methods A total of 81 patients with a Depressive Disorder (38 patients with a Mild Depressive Disorder and 45 with a Moderate-Severe disorder) and 79 healthy individuals were examined. All were asked to indicate, in a questionnaire, the time of awakening, of falling asleep, of maximum appetite, of maximum energy and of maximum mental fo- cusing, during "Adolescence" (12-15 years), "Youth" (16-20 years) and "Present condition" periods. Results from depressive patients and healthy individuals were compared by Student t test. Results from patients with a Mild Depressive Disorder and or a Moderate-Severe Depressive Disorder were also compared. Results
Temperaments are permanent variations of personality, traits and ways of reacting that characterize individuals and remain constant throughout several diverse situations. Temperaments play a crucial role in determining emotional reactions, therefore several temperamental models attempted to establish relationship between temperaments and affective disorders. According to the model of Akiskal, affective temperaments are subclinical and subaffective trait-like manifestations of affective disorders. Unlike several models of temperament which were developed theoretically in order to describe healthy human functioning, and were later extrapolated to also capture the pathological domains of mental and behavioral features, the model of affective temperaments was developed on Kraepelinian and Kretschmerian traditions and based on the observation of patients with mood disorders and their healthy first degree relatives and from that point broadened to encompass also the subclinical and nonclinical domains of affective reactivity. There is accumulating evidence concerning the development of affective temperaments based on their adaptive evolutionary characteristics and genetic background, and normative data from large national studies on general and healthy samples indicate their universal characteristics. Studies in affective patient populations indicate that the relationship between affective temperaments and affective illness is more complex than a simple extrapolation from psychopathology and mental health, and affective temperaments may play a patoplastic role in mood disorders determining their evolution, clinical features, main characteristics and outcome. A large body of data on affective temperaments has been published during the last decade, deserving a critical analysis presented in this review.
Hypertension Research, official publication of the Japanese Society of Hypertension, publishes papers reporting original clinical and experimental research in the field of hypertension and related cardiovascular diseases.
We examined the seasonal variation in human birth and infant survival rates in pre-modern Finland. If survival probabilities of children born during different seasons of the year differ and if timing of reproduction has been affected by natural selection, periodic variation in environment could have led to reproduction during the season of best infant survival expectations. Significant seasonal variation in both birth rate and survival probability was found, but the monthly birth and survival rates of newborn were uncorrelated. Hence, if there was any tendency to maximise the reproductive success, increase in some other component of fitness than the infant survival was probably targeted. The effect of major holidays on the birth rate was proved to be notable, suggesting that although the basis for seasonal variation in birth rate was biological, sociocultural factors had an impact on the timing of reproduction in humans. The overall mortality of infant boys exceeded that of infant girls in all seasons. This difference was smallest during the time of best food supplies, indicating that the development of males was less buffered against environmental disturbances than that of females.
The initial Global Burden of Disease study found that depression was the fourth leading cause of disease burden, accounting for 3.7% of total disability adjusted life years (DALYs) in the world in 1990.
To present the new estimates of depression burden for the year 2000.
DALYs for depressive disorders in each world region were calculated, based on new estimates of mortality, prevalence, incidence, average age at onset, duration and disability severity.
Depression is the fourth leading cause of disease burden, accounting for 4.4% of total DALYs in the year 2000, and it causes the largest amount of non-fatal burden, accounting for almost 12% of all total years lived with disability worldwide.
These data on the burden of depression worldwide represent a major public health problem that affects patients and society.
Recently, the adaptive significance of maternal effects has been increasingly recognized. No longer are maternal effects relegated as simple `troublesome sources of environmental resemblance' that confound our ability to estimate accurately the genetic basis of traits of interest. Rather, it has become evident that many maternal effects have been shaped by the action of natural selection to act as a mechanism for adaptive phenotypic response to environmental heterogeneity. Consequently, maternal experience is translated into variation in offspring fitness.
The Seasonal Pattern Assessment Questionnaire (SPAQ) was mailed to a sample population balanced for sex and randomly selected from local telephone directories in four areas: Nashua, NH, New York, NY, Montgomery County, MD, and Sarasota, FL. On the basis of responses to this questionnaire, prevalence rates of winter seasonal affective disorder (winter SAD), summer seasonal affective disorder (summer SAD), and subsyndromal winter SAD were estimated for the four areas. Rates of winter SAD and subsyndromal SAD were found to be significantly higher at the more northern latitudes, while no correlation was found between latitude and summer SAD. The positive correlation between latitude and prevalence of winter SAD applied predominantly to the age groups over 35.
Seasonal affective disorder (SAD) is a syndrome characterized by recurrent depressions that occur annually at the same time each year. We describe 29 patients with SAD; most of them had a bipolar affective disorder, especially bipolar II, and their depressions were generally characterized by hypersomnia, overeating, and carbohydrate craving and seemed to respond to changes in climate and latitude. Sleep recordings in nine depressed patients confirmed the presence of hypersomnia and showed increased sleep latency and reduced slow-wave (delta) sleep. Preliminary studies in 11 patients suggest that extending the photoperiod with bright artificial light has an antidepressant effect.
Artificial bright light presents a promising nonpharmacological treatment for seasonal affective disorder. Past studies, however, have lacked adequate placebo controls or sufficient power to detect group differences. The importance of time of day of treatment--specifically, morning light superiority--has remained controversial.
This study used a morning x evening light crossover design balanced by parallel-group controls, in addition to a nonphotic control, negative air ionization. Subjects with seasonal affective disorder (N = 158) were randomly assigned to 6 groups for 2 consecutive treatment periods, each 10 to 14 days. Light treatment sequences were morning-evening, evening-morning, morning-morning, and evening-evening (10,000 lux, 30 min/d). Ion density was 2.7 x 10(6) (high) or 1.0 x 10(4) (low) ions per cubic centimeter (high-high and low-low sequences, 30 min/d in the morning).
Analysis of depression scale percentage change scores showed low-density ion response to be inferior to all other groups, with no other group differences. Response to evening light was reduced when preceded by treatment with morning light, the sole sequence effect. Stringent remission criteria, however, showed significantly higher response to morning than evening light, regardless of treatment sequence.
Bright light and high-density negative air ionization both appear to act as specific antidepressants in patients with seasonal affective disorder. Whether clinical improvement would be further enhanced by their use in combination, or as adjuvants to medication, awaits investigation.
Many functions have been suggested for low mood or depression, including communicating a need for help, signaling yielding in a hierarchy conflict, fostering disengagement from commitments to unreachable goals, and regulating patterns of investment. A more comprehensive evolutionary explanation may emerge from attempts to identify how the characteristics of low mood increase an organism's ability to cope with the adaptive challenges characteristic of unpropitious situations in which effort to pursue a major goal will likely result in danger, loss, bodily damage, or wasted effort. In such situations, pessimism and lack of motivation may give a fitness advantage by inhibiting certain actions, especially futile or dangerous challenges to dominant figures, actions in the absence of a crucial resource or a viable plan, efforts that would damage the body, and actions that would disrupt a currently unsatisfactory major life enterprise when it might recover or the alternative is likely to be even worse. These hypotheses are consistent with considerable evidence and suggest specific tests.
Month of birth influences adult life expectancy at ages 50+. Why? In two countries of the Northern Hemisphere-Austria and Denmark-people born in autumn (October-December) live longer than those born in spring (April-June). Data for Australia show that, in the Southern Hemisphere, the pattern is shifted by half a year. The lifespan pattern of British immigrants to Australia is similar to that of Austrians and Danes and significantly different from that of Australians. These findings are based on population data with more than a million observations and little or no selectivity. The differences in lifespan are independent of the seasonal distribution of deaths and the social differences in the seasonal distribution of births. In the Northern Hemisphere, the excess mortality in the first year of life of infants born in spring does not support the explanation of selective infant survival. Instead, remaining life expectancy at age 50 appears to depend on factors that arise in utero or early in infancy and that increase susceptibility to diseases later in life. This result is consistent with the finding that, at the turn of the last century, infants born in autumn had higher birth weights than those born in other seasons. Furthermore, differences in adult lifespan by month of birth decrease over time and are significantly smaller in more recent cohorts, which benefited from substantial improvements in maternal and infant health.
This study was carried out to quantify secular trends in seasonal variation in births in Malta, a small Mediterranean country where the vast proportion of births occur in wedlock due to a predominantly Roman Catholic population. It also related such variations to seasonal variation in marriages. Annual seasonal peaks of marriages and births were analysed over the period 1950-1996 by X11 ARIMA. A significant peak in marriages (n = 111,932) in the third quarter of the year was found for almost the entire period under study. This was paralleled by a peak in births (n = 299,558) for the period 1970-1996, which lagged after the peak in marriages by 13-14 months. For the period 1994-1996, when monthly data for monthly pregnancies were available by pregnancy order, the peak in births was caused by first pregnancies only. Seasonal patterns in births occur almost universally due to cultural and/or biometeorological factors. The best known patterns include those of the southern United States, where births decline in April and May, and in northern Europe, where births peak in March and April. In Malta, the late summer peak in births appears to be due to a practical and planned approach by Maltese couples to contraceptive planning, probably influenced by the Roman Catholic ethos and social pressures, with unprotected intercourse occurring only after marriage. In Malta, birth control, albeit by so-called natural methods, was introduced in the 1960s. Prior to this period, births peaked towards the beginning/end of the year, and this may be the more natural seasonality of births in Malta.
To longitudinally examine cognitive-behavioral correlates of seasonal affective disorder (SAD), the authors assessed women with a history of SAD and nondepressed, matched controls across fall, winter, and summer. SAD history participants reported more automatic negative thoughts throughout the year than controls and demonstrated a progression from decreased activity enjoyment during fall to reduced activity frequency during winter. Ruminative response style, measured in fall, predicted symptom severity during the winter. Across assessments, SAD history women endorsed greater depressive affect in response to low light intensity stimuli than to bright or ambiguous intensity stimuli, but less depressed mood to bright light stimuli than controls. These results suggest that the cognitive-behavioral factors related to nonseasonal depression may play a role in SAD.
The authors attempted to estimate the occurrence, frequency, and pattern (winter versus summer) of seasonal affective disorder in African American college students. They hypothesized that winter seasonal affective disorder would be more prevalent than summer seasonal affective disorder.
Undergraduate and graduate college students who identified themselves as African Americans living in the Washington, D.C., metropolitan area were invited to participate in the study. The Seasonal Pattern Assessment Questionnaire was used to calculate a global seasonality score and to estimate the frequency of seasonal affective disorder and subsyndromal seasonal affective disorder. The frequency of the summer versus winter pattern of seasonality of seasonal affective disorder was compared by using multinomial probability distribution tests. The effects of gender and the awareness of seasonal affective disorder were evaluated with a two-way analysis of variance.
Of 646 students who were invited to participate, 597 returned the questionnaires, and 537 (83.1%) fully completed them. Winter seasonal affective disorder was significantly more prevalent than summer seasonal affective disorder. The mean global seasonality score was 8.3 (SD=5.3). The majority of the subjects (80%) were not aware of the existence of seasonal affective disorder.
The authors found that the frequency, magnitude, and pattern of seasonality of mood in African American students were similar to those previously reported in the general population at similar latitude, but that awareness of the existence of seasonal affective disorder, a condition with safe and effective treatment options, was lower.
• Seasonal affective disorder (SAD) is a syndrome characterized by recurrent depressions that occur annually at the same time each year. We describe 29 patients with SAD; most of them had a bipolar affective disorder, especially bipolar II, and their depressions were generally characterized by hypersomnia, overeating, and carbohydrate craving and seemed to respond to changes in climate and latitude. Sleep recordings in nine depressed patients confirmed the presence of hypersomnia and showed increased sleep latency and reduced slow-wave (delta) sleep. Preliminary studies in 11 patients suggest that extending the photoperiod with bright artificial light has an antidepressant effect.
Numerous studies document lower levels of depression among adults with higher education, but little is known about the way in which the association varies over the life course. Do depression levels diverge or converge across educational strata with age? This study investigates how the association between education and depression changes with age and tests the extent to which these changes are accounted for by physical health problems, widowed status, employment status, coping resources, household income, and financial strain. Data for this investigation come from the Work, Family, and Well-Being Study, 1990, a nationally representative sample of 2,031 adults aged 18 to 90 interviewed by telephone. Findings indicate that the association between depression and education strengthens with increasing age. Physical health problems among adults with lower education account for most of the diverging gap in depression. These results show that an integration of insights from the stress paradigm and the life course perspective can lead to a fuller understanding of socioeconomic inequality and its influence on psychological functioning.
The season of birth in man appears to be meteorologically controlled thought minor minima of cultural origin are also apparent. The change of conception may be temperature dependent. The periodicity in the Southern Hemisphere is the reverse of that of the northern one. The Moslem Mediterranean region exhibits patters similar to southern Europe, as does Central America. The United States, Canada and Puerto Rico have a pattern that appears to be anomalous compared to the rest of the world. The seasonality of birth is a sensitive indicator of certain cultural and biological phenomena. The amplitude is increased by illegitimacy, death, belonging to a race other than Caucasian, war, depression, lack of industrialization, poverty of rural living. There is some indication, over time, that the mere process of urbanization and industrialization can cause the amplitude to behave in an erratic fashion. An hypothesis has been suggested to explain changes that have occurred during the past century. It is thought that the effect of urbanization is responsible for the change and in part the improvement of the standard of living has also be an influence. Spain and Sweden have shown no major variation in their season of birth for the period of time for which there are data.
The aim of the present study was to explore winter pattern seasonality of mood by investigating its Five Factor Model (FFM) correlates. The study was an advance on existing research in that seasonality was measured not as a retrospective self-description of mood variation, but as a prospective pattern of current mood states in winter and summer (across two years). Based on contemporary theorizing about the structure and function of mood, Positive Affect (PA) was the mood construct selected for measurement. A seasonality score was calculated for each participant as the difference between summer mood levels and winter mood levels. The NEO-FFI was administered at all four waves. Three hundred and three respondents from a random community sample in Melbourne, Australia, provided complete data. Regression analyses found that the adaptive trait Openness to Experience (O) was specifically associated with the tendency towards lowered mood in winter relative to summer. The vulnerability trait Neuroticism (N) was not a directional predictor of winter pattern seasonality, but was the sole predictor of absolute seasonality score. Findings are discussed in terms of two affective processes that may be involved in mood variation across the seasonal time frame: adaptive environmental sensitivity and endogenous mood variability. Copyright © 2002 John Wiley & Sons, Ltd.
A series of eight hypotheses is presented, based on the results of current research, concerning the responsiveness of the human ovary to constitutional and environmental variables. These hypotheses are motivated by a theoretical position that seeks to understand human reproductive physiology as the product of natural selection. The hypotheses are: (1) Ovarian responsiveness occurs along a graded continuum. (2) The graded continuum of response forms a final common pathway for various “stresses.” (3) Ovarian function tracks energy balance, not simply nutritional status. (4) Ovarian function tracks aerobic activity independently of energy balance. (5) Additive interactions characterize the interaction of constitutional and environmental factors modulating ovarian function. (6) Reproductive maturation is synchronized with skeletal maturation, especially of the pelvis. (7) Peak ovarian function is not ordinarily achieved until the early twenties. (8) Late reproductive maturation is associated with a slower rise in indices of ovarian function with age, and a lower level of ovarian function in adulthood. Together, these hypotheses provide for two, non-exclusive theories of facultative modulation of female reproductive effort. One theory views ovarian function as responsive to the prospects for positive reproductive outcome as these may be affected by maternal age, maturation, energy balance, and activity level. The second theory views ovarian function as responsive in a similar way to the need to maintain long-term maternal energy balance.
During the first half of this century, the seasonal pattern of births in European countries showed a major peak in the spring and a minor peak in the autumn. In contrast, the pattern in the US was of a minor peak in spring and a major peak in autumn. Over the last 20 years, the pattern in England and Wales has changed to resemble the US pattern, and the same seems to be true of several other European countries. A hypothesis is offered to account for the difference between the European and the US patterns and for the change from one to the other in some countries. The magnitude of seasonality correlates positively with latitude: it is suggested that this is partially consequent on variation in luminosity.
PIP
During the first half of the century, the seasonal pattern of births in European countries showed a major peak in spring and a minor peak in autumn. Over the last 20 years the pattern in England, Wales and other European countries has changed to a US birth rate pattern which has only 1 broad peak from the summer to early fall. Many hypothesized factors may affect seasonal birth rates. A new hypothesis which expounds a festival effect of Thanksgiving to Christmas, where couples that are separated by work or choice often make time to be together and therefore improve coital frequencies is described. The magnitude of seasonality correlates positively with latitude: it is suggested that this is partially consequent on a variation in luminosity.
Earlier studies on the seasonality of births indicate that a major peak occurs in August and September and a minor peak in January and February. This study uses the 1984 Canadian Fertility Survey data on reproductive history to examine birth and pregnancy seasonalities, and shows that the 'worst' months for births are January and February and the 'best' months are March, April and May. There is no systematic pattern in the seasonality of pregnancies, possibly because effective birth control allows couples to plan the timing of births.
Patterns of seasonal changes in mood and behavior in Montgomery County, Maryland, were evaluated in randomly selected household samples by lay interviewers using a telephone version of the Seasonal Pattern Assessment Questionnaire. The method for selecting the sample unit was random-digit dialing. We found that 92% of the survey subjects noticed seasonal changes of mood and behavior to varying degrees. For 27% of the sample seasonal changes were a problem and 4.3% to 10% of subjects, depending on the case-finding definition, rated a degree of seasonal impairment equivalent to that of patients with seasonal affective disorder. The seasonal pattern of "feeling worst" exhibited a bimodal distribution with a greater winter and a substantially lower summer peak (ratio, 4.5:1). Younger women who have a problem with seasonal changes and who feel worse on short days tended to exhibit the highest seasonality scores. It is apparent from our study that seasonal affective disorder represents the extreme end of the spectrum of seasonality that affects a large percentage of the general population. The influence of environmental factors on mood disorders and mood changes in the general population might provide valuable insight into pathogenesis, treatment, and prevention of affective illness.
The long-term course of seasonal affective disorder has not been well studied.
Using the Structured Clinical Interview for DSM-III-R, we interviewed 75% of a sample of 124 subjects diagnosed from five to eight years previously as fulfilling DSM-III-R criteria for recurrent major affective disorder, seasonal pattern.
In the follow-up period, 38% of the sample continued to fulfil DSM-III-R criteria for seasonal illness; 28% had recurrent major depressive disorder, but no longer displayed a seasonal pattern; 18% were completely well with no further depression; 6% had subsyndromal symptoms; and 5%, although not meeting DSM-III-R criteria for seasonal illness, were still displaying constant periodicity. A short duration of index episode and a high frequency of illness predicted a continuing seasonal course of illness.
Diagnostic criteria for seasonal affective disorder need to be further refined, possibly restrictively, if they are to be used to predict the future course of seasonal illness.
Almost all human populations exhibit seasonal variation in births, owing mostly to seasonal variation in the frequency of conception. This review focuses on the degree to which environmental factors like nutrition, temperature and photoperiod contribute to these seasonal patterns by acting directly on the reproductive axis. The reproductive strategy of humans is basically that of the apes: Humans have the capacity to reproduce continuously, albeit slowly, unless inhibited by environmental influences. Two, and perhaps three, environmental factors probably act routinely as seasonal inhibitors in some human populations. First, it seems likely that ovulation is regulated seasonally in populations experiencing seasonal variation in food availability. More specifically, it seems likely that inadequate food intake or the increased energy expenditure required to obtain food, or both, can delay menarche, suppress the frequency of ovulation in the nonlactating adult, and prolong lactational amenorrhea in these populations on a seasonal basis. This action is most easily seen in tropical subsistence societies where food availability often varies greatly owing to seasonal variation in rainfall; hence births in these populations often correlate with rainfall. Second, it seems likely that seasonally high temperatures suppress spermatogenesis enough to influence the incidence of fertilization in hotter latitudes, but possibly only in males wearing clothing that diminishes scrotal cooling. Since most of our knowledge about this phenomenon comes from temperate latitudes, the sensitivity of spermatogenesis in both human and nonhuman primates to heat in the tropics needs further study. It is quite possible that high temperatures suppress ovulation and early embryo survival seasonally in some of these same populations. Since we know less than desired about the effect of heat stress on ovulation and early pregnancy in nonhuman mammals, and nothing at all about it in humans or any of the other primates, this is an important area for future research. Third, correlational data suggest that there may be some degree of regulation of reproduction by photoperiod in humans at middle to higher latitudes. Populations at these latitudes often show a peak in presumed conceptions associated with the vernal equinox. On the other hand, evidence gathered by neuroendocrinologists tends to argue against reproductive photoresponsiveness in humans.
Basic epidemiologic prevalence data are presented on sex differences in DSM-III-R major depressive episodes (MDE). The data come from the National Comorbidity Survey (NCS), the first survey in the U.S. to administer a structured psychiatric interview to a nationally representative sample of the general population. Consistent with previous research, women are approximately 1.7 times as likely as men to report a lifetime history of MDE. Age of onset analysis shows that this sex difference begins in early adolescence and persists through the mid-50s. Women also have a much higher rate of 12-month depression than men. However, women with a history of depression do not differ from men with a history of depression in either the probability of being chronically depressed in the past year or in the probability of having an acute recurrence in the past year. This means that the higher prevalence of 12-month depression among women than men is largely due to women having a higher risk of first onset. The implications of these results for future research are discussed in a closing section of the paper.
Seasonal rhythms in mood and behavior (seasonality) have been reported to occur in the general population. Seasonal affective disorder, a clinically diagnosed syndrome, is believed to represent the morbid extreme of a spectrum of seasonality. Two types of seasonality have been clinically described: one characterized by a winter pattern and a second by a summer pattern of depressive mood disturbance.
By using methods of univariate and multivariate genetic analysis, we examined the relative contribution of genetic and environmental factors to the risk of seasonality symptoms that were assessed by a mailed questionnaire of 4639 adult twins from a volunteer-based registry in Australia.
Seasonality was associated with a winter rather than a summer pattern of mood and behavioral change. In each behavioral domain (ie, mood, energy, social activity, sleep, appetite, and weight), a significant genetic influence on the reporting of seasonal changes was found. Consistent with the hypothesis of a seasonal syndrome, genetic effects were found to exert a global influence across all behavioral changes, accounting for at least 29% of the variance in seasonality in men and women.
There is a tendency for seasonal changes in mood and behavior to run in families, especially seasonality of the winter type, and this is largely due to a biological predisposition. These findings support continuing efforts to understand the role of seasonality in the development of mood disorders.
The Seasonal Pattern Assessment Questionnaire (SPAQ) was administered to a sample of students, faculty, and staff at a large state university in central Texas. Estimated prevalence rates of winter seasonal affective disorder (SAD) and subsyndromal winter SAD (S-SAD) derived from their SPAQ responses were considerably higher than expected, given the relatively low latitude of the area. Generally consistent with earlier findings, women experienced greater seasonal change in mood and behavior than men, and older individuals experienced less seasonal change than younger individuals.
To determine whether a predominantly summer-focussed pattern of seasonal affective disorder (SAD) exists in tropical northern Australia.
A mail survey containing a modified form of the Seasonal Pattern Assessment Questionnaire (SPAQ) was administered to 176 households in the city of Townsville (latitude: 19 degrees south).
Using previously reported screening criteria, 9% of respondents reported a degree of summer impairment indicative of SAD, while the incidence rate for winter SAD was 1.7%. This summer-winter ratio is typically reversed in more temperate latitudes.
Excessive heat and humidity were reported to be the two most influential environmental factors affecting mood and behaviour. It is likely that respondents meeting criteria for summer SAD represent the extreme end of a spectrum of summer-related mood and behaviour change that affects many individuals in northern Australia. Strategies for further clinical and epidemiological research on SAD in tropical climates are proposed.
The study estimated gender differences in the magnitude of genetic and environmental influence in seasonal mood change. The self-report Seasonal Pattern Assessment Questionnaire (SPAQ) was completed by 339 volunteer reared-together twinpairs (187 monozygotic pairs, 152 dizygotic pairs) and analysed using biometric genetic models. The SPAQ yields a global seasonality score (GSS) which is an index of change in sleep patterns, social activities, mood, weight, appetite, and energy level. The GSS was significantly heritable among males and females, estimated to account for 69% and 45% of the total variance, respectively. For the individual symptoms, changes in sleep patterns, social activities, mood, appetite, and energy levels were accounted for primarily by additive genetic effects in both males (median, 45.5%) and females (median, 30.5%). For both sexes, weight changes were not heritable. Sex-by-genotype analyses suggested that the genetic factors influencing female seasonality may not be the same as those influencing male seasonality.
To determine whether age at menopause is related to size at birth.
A follow-up study of two groups of women whose size at birth was recorded.
Hertfordshire and Sheffield, England.
755 women aged 60-71 years born in Hertfordshire; 235 women aged 40-42 years born in the Jessop Hospital, Sheffield.
Age at natural menopause or serum follicle stimulating hormone concentration greater than 25 IU/ml.
Age at menopause was unrelated to birth weight. However, it occurred at a younger age in women who had low weight at 1 year. This was independent of their body weight and smoking habits. In the population of younger women those who had had an early menopause tended to have been short at birth, with a high ponderal index (birth weight/length3).
Growth retardation in late gestation, leading to shortness at birth and low weight gain in infancy, may be associated with a reduced number of primordial follicles in the ovary leading in turn to an earlier menopause.
Despite the long history in medicine, the pathophysiological mechanism(s) of seasonal affective disorder (SAD) remain largely unknown. By employing a meta-analytic methodology, the authors of this study attempted to verify the validity of different pathophysiological mechanism(s) proposed for SAD. The findings showed that for phototherapy of medium light intensity, a combination of morning-evening therapy regime yielded the best therapeutic effect, and the antidepressant effect of the morning-evening light regime was superior to a single pulse of light administered at other times of day. Furthermore, the data showed that the antidepressant effect of a single pulse of light was similar for morning, midday, and evening light. These findings supported the photon-count hypothesis and refuted the proposed photoperiod, melatonin, and phase-shifting models of SAD.
We hypothesized that if prenatal caloric restriction due to nutritional deprivation had affected development of the organs responsible for producing and regulating female reproductive hormones, a woman's fertility would be impaired.
Women born in Amsterdam from August 1, 1944, through April 15, 1946, a period encompassing a severe 5-month famine, were identified (n = 700; 85% response rate). Date of birth and vital status of all offspring were ascertained by home interview between 1987 and 1991. Famine exposure was inferred from the mother's date of birth.
Of the study participants, 74 (10.6%) had no children. The remainder reported 1334 off-spring (1294 singletons, 20 pairs of twins), of whom 14 were stillborn and 22 died in the first 7 days of life. There was no detectable effect of famine exposure on age at menarche, the proportion having no children, age at first delivery, or family size. An excess of perinatal deaths occurred among offspring of famine-exposed women, particularly those exposed in their third trimester.
Acute famine exposure in utero appears to have no adverse consequences for a woman's fertility. The excess perinatal mortality in the second generation is unexplained and should be confirmed by other studies.
The aim of the study is to investigate the relationship between the prevalence of SAD and latitude.
An overview of the epidemiological literature on the prevalence of SAD is given and studies relevant for the latitudinal dependency of prevalence will be analyzed and discussed.
The mean prevalence of SAD is two times higher in North America compared to Europe. Over all prevalence studies, the correlation between prevalence and latitude was not significant. A significant positive correlation was found between prevalence and latitude in North America. For Europe there was a trend in the same direction.
The influence of latitude on prevalence seems to be small and other factors like climate, genetic vulnerability and social-cultural context can be expected to play a more important role. Additional controlled studies taking these factors into account are necessary to identify their influence.
To examine the effect of sex, latitude, and behavior problems on symptoms related to pediatric seasonal affective disorder among seventh and ninth graders.
A school survey including a modified version of the Seasonal Pattern Assessment Questionnaire was carried out in 2 Finnish cities located in the 60th and 67th northern latitudes. Altogether 1,458 questionnaires were analyzed, representing 89% of the target population.
Seasonal changes in mood and behavior were commonly reported among seventh and ninth graders. A high Global Seasonality score (> 95th percentile) was associated with female gender and emotional and hyperactivity symptoms. During February and March, girls living in the 67th latitude reported more seasonal distress than girls living at the 60th latitude.
It is important to recognize pediatric seasonal affective disorder and related problems among adolescents. Seasonal alterations in child and adolescent behavior are not well understood and need to be investigated more thoroughly.
Given that seasonality can be conceptualized along a developmental continuum, it is surprising that the college population has been largely excluded from previous epidemiological research on Seasonal Affective Disorder (SAD). In this study, college students completed the Seasonal Pattern Assessment Questionnaire (SPAQ) and Beck Depression Inventory twice during either the Fall or Spring academic semester. SAD prevalence rates were similar to those of nearby adult samples. The SPAQ demonstrated high test-retest reliability when administered during different seasons; however, gender differences only emerged during winter SPAQ administrations.
The degree to which seasonal changes affect mood, energy, sleep, appetite, food preference, or the wish to socialize with other people has been called seasonality. Seasonal affective disorder (SAD), a condition where depressions in fall and winter alternate with non-depressed periods in spring and summer, is the most marked form of seasonality. Several lines of evidence suggest that genetic factors play an important role in the etiology of seasonality and SAD. Millions of years of evolution and adaptation have optimized human biochemical and physiological systems for function and survival under equatorial environmental conditions. Modern humans began their migration out of Africa only about 150 000 years ago. Little change in our 'equatorial' systems might have been expected over this relatively short evolutionary time-span. The author suggests that a genetic susceptibility to seasonal changes in mood and behavior is a genetic predisposition to an insufficient adaptation to temperate and high latitudes.
Pleiotropy refers to the ability of a single gene to influence multiple traits. A polymorphism in the regulatory region of the serotonin transporter gene (5-HTTLPR) has previously been found to be associated both with the personality trait of neuroticism and with seasonal changes in mood and behavior, or seasonality. Hypothesizing that the contribution of the serotonin transporter gene to seasonality is specific, i.e. independent of neuroticism, we measured 5-HTTLPR genotypes and both psychological traits in 236 healthy volunteers. The results indicated that the 5-HTTLPR contributions to variation in the two traits are largely independent; approximately three-quarters of the effect of the gene on seasonality are not related to its effects on neuroticism. Moreover, the gene has a larger effect on the covariation between neuroticism and seasonality than it does on either trait alone. Sibling-pair analysis confirmed that the effects of the 5-HTTLPR are due to genetic pleiotropy rather than population stratification.
Case records of the patients with major affective disorders (ICD-10 criteria), seen over a 5 year period in a busy clinic in North India were examined for Seasonal Affective Disorder (SAD) as per DSM-III-R criteria. In addition, seasonality of episodes of all affective disorders was also studied. Around 5.67% of the cases (n=44) retrospectively met the DSM-III-R criteria of SAD and predominant pattern was that of summer depression (n=18). There was also a consistent pattern of seasonal mania either in conjunction with seasonal depression (n=18) or in form of seasonal recurrent mania (n=11). None of the cases of depression showed any atypical vegetative features. In cases not meeting criteria for SAD (n=731), there was a trend for peaks for depressive episodes in winter followed by a smaller peak in summer months while manic episodes had peaks towards rainy and winter months. As compared to seasonal patterns of affective disorders in temperate zones, there was a general trend for opposite patterns of seasonality in SAD as well as in non-SAD. The findings are discussed in context of the climatic conditions of North India.
The association between depression and mortality has become a topic of interest. Little is known about the association between the course of depression and mortality. Methods: In an initially non-depressed cohort (N = 325) and a depressed cohort (N = 327), depression was measured using the Center for Epidemiologic Studies Depression scale (CES-D) at eight successive waves over a period of 3 years. Both cohorts were then followed with respect to mortality status for up to 3.5 additional years. Clinical course types as well as theoretical course type parameters (basic symptom levels, increases in symptoms and instability over time) were distinguished to study the effect of the course of depression on mortality.
Contrary to transient states of depression, both chronic depression and chronic intermittent depression predicted mortality at follow-up. Additionally, evidence was found that the effect on mortality is related to severity of depression; high basic symptom levels and increases in symptoms over time were predictive of mortality. A high degree of instability over time was not associated with mortality.
Since the mortality effect of depression is a function of both exposure time and symptom severity, more attention should be paid to the treatment of depression in order to prevent severe longstanding depression.
To expand and accelerate research on mood disorders, the National Institute of Mental Health (NIMH) developed a project to formulate a strategic research plan for mood disorder research. One of the areas selected for review concerns the development and natural history of these disorders. The NIMH convened a multidisciplinary Workgroup of scientists to review the field and the NIMH portfolio and to generate specific recommendations. To encourage a balanced and creative set of proposals, experts were included within and outside this area of research, as well as public stakeholders. The Workgroup identified the need for expanded knowledge of mood disorders in children and adolescents, noting important gaps in understanding the onset, course, and recurrence of early-onset unipolar and bipolar disorder. Recommendations included the need for a multidisciplinary research initiative on the pathogenesis of unipolar depression encompassing genetic and environmental risk and protective factors. Specifically, we encourage the NIMH to convene a panel of experts and advocates to review the findings concerning children at high risk for unipolar depression. Joint analyses of existing data sets should examine specific risk factors to refine models of pathogenesis in preparation for the next era of multidisciplinary research. Other priority areas include the need to assess the long-term impact of successful treatment of juvenile depression and known precursors of depression, in particular, childhood anxiety disorders. Expanded knowledge of pediatric-onset bipolar disorder was identified as a particularly pressing issue because of the severity of the disorder, the controversies surrounding its diagnosis and treatment, and the possibility that widespread use of psychotropic medications in vulnerable children may precipitate the condition. The Workgroup recommends that the NIMH establish a collaborative multisite multidisciplinary Network of Research Programs on Pediatric-Onset Bipolar Disorder to achieve a better understanding of its causes, course, treatment, and prevention. The NIMH should develop a capacity-building plan to ensure the availability of trained investigators in the child and adolescent field. Mood disorders are among the most prevalent, recurrent, and disabling of all illnesses. They are often disorders of early onset. Although the NIMH has made important strides in mood disorders research, more data, beginning with at-risk infants, children, and adolescents, are needed concerning the etiology and developmental course of these disorders. A diverse program of multidisciplinary research is recommended to reduce the burden on children and families affected with these conditions.
Seasonal affective disorder (SAD) is characterized by recurrent episodes of depression occurring regularly with the onset of winter.
The study was a prospective naturalistic follow-up of the emergence of symptoms of seasonal depression with the passage of time and change in seasons. Participants were screened during summer for SAD. Participants were excluded if they were depressed (BDI > 14) during the summer reruitment. Eligible participants prospectively monitored their mood and anxiety by completing the BDI and BAI every 2 weeks from 1 September through to the 31 March.
Forty-five participants met criterion for SAD were included in the final data analyses. Depression scores rose gradually over the 30 week period reaching a peak median score around weeks 22 to 24 (January-February). The 'hallmark' physiological symptoms (changes in sleep, appetite and fatigue) emerged earlier in the winter period than cognitive symptoms. The emergence of anxiety symptoms was highly correlated with depressive symptoms, although the median anxiety scores did not reach a clinically significant level. Low self-esteem and poor perceived social support were significantly related to an earlier onset in the emergence of depressive symptoms. Both these factors together resulted in the speediest onset of depression. Poor perceived social support, but not low self-esteem, was associated with earlier emergence of anxiety symptoms.
Physiological symptoms may activate negative cognitions in individuals with risk factors of low self-esteem and poor social support so that the disorder is precipitated earlier and is of longer duration.
Growth, survival, and breeding success of individuals in populations of wild mammals are influenced by the climatic and nutritional conditions that individuals experience during their early development. Recent findings have shown that early conditions also have consequences for subsequent survival and reproductive performance in humans. Environmental conditions which affect early development of individuals, such as the quality and quantity of nutrition received in utero and infancy, predict the onset of many chronic diseases in adulthood, affect longevity and may also influence a range of measures of reproductive performance in both food-limited and contemporary Western human populations. These associations are proposed to result from foetal programming, where a stimulus or insult during a critical period early in life may permanently affect body structure, physiology, and metabolism. Here I review studies showing how birthweight, season of birth, or exposure to prenatal starvation affect different aspects of an individual's subsequent reproductive success in humans and the growth, survival, and reproductive performance of the offspring produced. I show that early maternal and environmental conditions can have a large impact on human reproductive strategies and fitness that can span across generations.
Conditions experienced during early development affect human health and survival in adulthood, but whether such effects have consequences for fitness is not known. One surrogate for early conditions is month of birth, which is known to influence health and survival in many human populations. We show that in nineteenth century Canada, month of birth predicted a woman's fitness measured by the number of grandchildren produced, with the genetic contribution to the following generations by women born in different months differing by over seven grandchildren. This difference was mainly caused by differences in the reproductive rates of both mothers and their offspring, rather than differences in their survival. Women born in the best months of the year had longer reproductive lifespans, larger numbers of live births and raised more offspring to adulthood than those who were born in the worst months. Furthermore, the offspring of those women born in the best months also had greater reproductive rates, suggesting that month of birth also influenced a mother's ability to invest in her offspring. Our results suggest that early conditions may have important consequences for human lifetime reproductive performance within and between generations, and that timing of birth had large effects on fitness in this rural community.
We evaluated the occurrence of postnatal depression in general and during different seasons as part of a larger longitudinal mother-child follow-up study.
One hundred and eighty-five mothers, from the maternity wards of University Hospital of Oulu, Finland, completed a self-rating depression scale, the Edinburgh Postnatal Depression Scale (EPDS) twice: first at hospital 2-7 days after delivery and the second time at home 4 months after the delivery. Different psychosocial variables were mapped out to avoid any confounding factors. The year was divided in two separate ways: first, three different time periods were selected by the amount of sunlight: dark (October-January), intermediate (February, March, August, September) and light (April-July), and second, the year was divided by seasons. The results were analysed by the chi(2)-test for multinomials.
Sixteen percent (16.2) of mothers were scored as being depressed using 13 as a cut-off point immediately after the infant was born. Thirteen percent (13.0) were depressed measured 4 months postpartum. There was more mild depression in the autumn (ratio observed/expected 1,62; 95% confidence interval 1.05-2.19) immediately after delivery, using 10 as a cut-off, and less depression in the spring (0.27; 0.00-0.62) measured at home later, using 13 as a cut-off. When using classification by the amount of light there was more depression during the dark time (1.58; 1.05-2.11) immediately postpartum.
The group sizes and the amount of sample sizes collected within each month are quite small.
It should be borne in mind that seasonal changes and alterations in the amount of light might influence the occurrence of postnatal depression.
To date, there has been only limited information on factors associated with seasonal changes in mood and behaviour experienced by a random sample of Australians living in a continental temperate climate region. This paper identifies socio-demographic, psychological and personality factors associated with reporting higher levels of seasonality.
Information on seasonal change using the Seasonal Pattern Assessment Questionnaire (SPAQ) was obtained from 7485 persons in three age groups. Age and sex differences in seasonality scores were examined. Those meeting probable caseness for seasonal affective disorder were identified and compared with less-seasonal participants on a range of state and trait measures.
Levels of seasonality reported by survey participants were comparable to those reported in northern hemisphere studies of randomly selected community samples. However, these levels were significantly lower than other key studies outside Australia and previous Australian findings. Compared with less-seasonal participants, those reporting seasonal change had more current depressive and anxiety symptoms and higher levels of negative affect, regardless of season of interview.
This study is likely to over-estimate the number of participants who meet requirements for caseness for seasonal affective disorder.
Levels of seasonality experienced by a random sample of Australians living in a temperate climate are comparable to those reported by similar groups in the northern hemisphere. Importantly, this study found that those experiencing higher levels of seasonality had significantly more current depressive symptoms than less-seasonal participants across all seasons. These results raise questions about the usefulness of the SPAQ as a measure of seasonal variation in mood and behaviour.
Season of birth or seasonal changes in putative etiologic factors are thought to influence the development of several psychiatric illnesses. The aim of this investigation was to examine seasonal differences in the frequency of birth in a clinical sample of patients with seasonal affective disorder (SAD).
553 outpatients suffering from SAD-DSM-IV-defined depressive disorder with winter-type seasonal pattern-who had been diagnosed and treated at the Department of General Psychiatry (University of Vienna, Austria) between 1994 and 2003, were included in this evaluation. We compared the observed number of births in our sample with expected values calculated from the general population.
There was a significant deviation of the observed number of births from the expected values calculated on a monthly basis (p = .009). When comparing quarters (periods of 3 months), we found fewer births than expected in the first quarter of the year and a slight excess of births in the second and third quarters (p = .034). There were also more births in the spring/summer season and fewer than expected in fall and winter (p = .029). Interestingly, patients with melancholic depression were more frequently born in fall/winter and less often in spring/summer compared with patients with atypical depression (p = .008).
Besides genetic factors, season of birth or seasonal changes in environmental factors also could influence the development of SAD. In addition, birth effects seem to be dependent on the symptom profile of the patients, but further studies are needed to elucidate the underlying mechanisms of these observations.