This study aimed to a) assess whether genetic or environmental effects are of similar magnitude in the etiology of GAD in men and women, and b) investigate whether familial (genetic or common environmental) risk factors are the same in men and women, or whether there are gender-specific effects. We obtained a lifetime history of DSM-IIII-R GAD, via face-to-face and telephone interviews, from 3100 complete male-male, female-female, and male-female twin pairs, ascertained through a population-based registry. Biometrical twin modeling was utilized to estimate the relative contributions of genetic and environmental factors to liability for GAD, allowing for gender-specific effects. The familial aggregation of GAD in this sample was only modest. In the best-fitting models, the heritability of GAD was the same in men and women, estimated at about 15% to 20%, with no effects of gender-specific genes detected.
"GAD was diagnosed when the minimum duration of illness was 1-month rather than 6-month (18.2% for broader definition and 8.4% meeting criteria for the full diagnosis). We have shown that these approaches reflect the same continuum of liability as the fully syndromal disorders (Hettema et al., 2001; Kendler et al., 2001). Our estimates of lifetime prevalence for psychopathology were generally greater than those reported in previous studies (Kessler et al., 2005), which was because we utilized methods to encourage " effortful responding " with a semi-structured interview and assessed last-year history and a lifetime history of disorders before the last year in two separate sections, combining these to estimate lifetime prevalence. "
[Show abstract][Hide abstract] ABSTRACT: Previous studies have identified the relationship between parental loss and psychopathology later in life. However, this relationship varied depending on the kind of loss, the parent involved, and the type of psychopathology. In the present study, we examined the association between parental loss (any loss, death, and separation) during childhood and lifetime risk for seven common psychiatric and substance use disorders in a sample of 2605 male twins from the Virginia population-based twin registry. Using structural equation modeling (SEM), we also examined the extent to which the influence of parental loss contributes to adult psychopathology. Parental separation was associated with a wide range of adult psychopathology, whereas parental death was specifically associated with phobia and alcohol dependence. Maternal and paternal separations were almost equally associated with most forms of psychopathology. SEM suggested that parental loss accounted for about 10% of the variance of adult psychopathology, of which parental separation had the strongest impacts on risk for depression and drug abuse/dependence (11% of the total variance). Our findings suggest that early parental separation has stronger and wider effects on adult psychopathology than parental death.
Psychiatry Research 08/2014; 220(1-2). DOI:10.1016/j.psychres.2014.07.053 · 2.47 Impact Factor
"For example, in studies using Swedish Twin Registry data with the same or overlapping birth cohorts, heritability estimates were as follows : bipolar disorder, 79 % ; Alzheimer's disease, 78–79 % ; anorexia nervosa, 56 % ; major depressive disorder, 38 % ; and generalized anxiety disorder, 27 % (Kendler et al. 1995, 2006b ; Gatz et al. 1997, 2006 ; Bulik et al. 2006 ; Mackintosh et al. 2006). Also, in studies using adult Virginia Twin Registry data, heritability estimates were as follows : drug use disorder, 66 % ; alcohol dependence, 49 % ; major depressive disorder, 39 % ; panic disorder, 37 % ; and generalized anxiety disorder , 22 % (Kendler & Prescott, 1999 ; Hettema et al. 2001b ; Kendler et al. 2001, 2003). "
[Show abstract][Hide abstract] ABSTRACT: Psychiatric conditions in which symptoms arise involuntarily ('diseases') might be assumed to be more heritable than those in which choices are essential (behavioral disorders). We sought to determine whether psychiatric 'diseases' (Alzheimer's disease, schizophrenia, and mood and anxiety disorders) are more heritable than behavioral disorders (substance use disorders and anorexia nervosa).
We reviewed the literature for recent quantitative summaries of heritabilities. When these were unavailable, we calculated weighted mean heritabilities from twin studies meeting modern methological standards.
Heritability summary estimates were as follows: bipolar disorder (85%), schizophrenia (81%), Alzheimer's disease (75%), cocaine use disorder (72%), anorexia nervosa (60%), alcohol dependence (56%), sedative use disorder (51%), cannabis use disorder (48%), panic disorder (43%), stimulant use disorder (40%), major depressive disorder (37%), and generalized anxiety disorder (28%).
No systematic relationship exists between the disease-like character of a psychiatric disorder and its heritability; many behavioral disorders seem to be more heritable than conditions commonly construed as diseases. These results suggest an error in 'common-sense' assumptions about the etiology of psychiatric disorders. That is, among psychiatric disorders, there is no close relationship between the strength of genetic influences and the etiologic importance of volitional processes.
Psychological Medicine 05/2010; 41(1):33-40. DOI:10.1017/S003329171000084X · 5.94 Impact Factor
"Following criticisms of the questionable clinical utility of the current duration criterion in defining GAD (Rickels & Rynn, 2001), a number of empirical studies in western countries have recently addressed this question. Taken together, they suggest that GAD lasting one month is comparable to GAD lasting 6 or more months in sociodemographic characteristics, clinical course, pattern of comorbidity, functional impairment, antecedent childhood adversity, and heritability (Kendler et al., 1992; Kendler et al., 1994; Bienvenu et al., 1998; Maier et al., 2000; Carter et al., 2001; Hettema et al., 2001; Kessler et al., 2005; Angst et al., 2006) Such findings have led a number of experts to call for shortening the duration criterion of GAD in DSM-V (Bienvenu et al., 1998; Rickels & Rynn, 2001; Kessler et al., 2005; Angst et al., 2006; Ruscio et al., 2007). Before this change can be considered seriously, however, additional data are needed on at least two fronts. "
[Show abstract][Hide abstract] ABSTRACT: A number of western studies have suggested that the 6-month duration requirement of generalized anxiety disorder (GAD) does not represent a critical threshold in terms of onset, course, or risk factors of the disorder. No study has examined the consequences of modifying the duration requirement across a wide range of correlates in both developed and developing countries.
Population surveys were carried out in seven developing and 10 developed countries using the WHO Composite International Diagnostic Interview (total sample=85,052). Prevalence and correlates of GAD were compared across mutually exclusive GAD subgroups defined by different minimum duration criteria.
Lifetime prevalence estimates for GAD lasting 1 month, 3 months, 6 months and 12 months were 7.5%, 5.2%, 4.1% and 3.0% for developed countries and 2.7%, 1.8%, 1.5% and 1.2% for developing countries, respectively. There was little difference between GAD of 6 months' duration and GAD of shorter durations (1-2 months, 3-5 months) in age of onset, symptom severity or persistence, co-morbidity or impairment. GAD lasting >or=12 months was the most severe, persistently symptomatic and impaired subgroup.
In both developed and developing countries, the clinical profile of GAD is similar regardless of duration. The DSM-IV 6-month duration criterion excludes a large number of individuals who present with shorter generalized anxiety episodes which may be recurrent, impairing and contributory to treatment-seeking. Future iterations of the DSM and ICD should consider modifying the 6-month duration criterion so as to better capture the diversity of clinically salient anxiety presentations.
Psychological Medicine 07/2009; 39(7):1163-76. DOI:10.1017/S0033291708004807 · 5.94 Impact Factor
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