[Show abstract][Hide abstract]ABSTRACT: Objective:
The association between physical activity and affect found in longitudinal observational studies is generally small to moderate. It is unknown how this association generalizes to individuals. The aim of the present study was to investigate interindividual differences in the bidirectional dynamic relationship between physical activity and affect, in depressed and nondepressed individuals, using time-series analysis.
A pair-matched sample of 10 depressed and 10 nondepressed participants (mean age = 36.6, SD = 8.9, 30% males) wore accelerometers and completed electronic questionnaires 3 times a day for 30 days. Physical activity was operationalized as the total energy expenditure (EE) per day segment (i.e., 6 hr). The multivariate time series (T = 90) of every individual were analyzed using vector autoregressive modeling (VAR), with the aim to assess direct as well as lagged (i.e., over 1 day) effects of EE on positive and negative affect, and vice versa.
Large interindividual differences in the strength, direction and temporal aspects of the relationship between physical activity and positive and negative affect were observed. An exception was the direct (but not the lagged) effect of physical activity on positive affect, which was positive in nearly all individuals.
This study showed that the association between physical activity and affect varied considerably across individuals. Thus, while at the group level the effect of physical activity on affect may be small, in some individuals the effect may be clinically relevant. (PsycINFO Database Record
[Show abstract][Hide abstract]ABSTRACT: Replication has been poor for previously reported candidate genes involved in Major Depressive Disorder (MDD). One possible reason is phenotypic and genetic heterogeneity. The present study replicated genetic associations with MDD as defined in DSM-IV and with a more narrowly defined MDD subtype with a chronic and severe course. We first conducted a systematic review of genetic association studies on MDD published between September 2007 and June 2012 to identify all reported candidate genes. Genetic associations were then tested for all identified single nucleotide polymorphisms (SNPs) and the entire genes using data from the GAIN genome-wide association study (MDD: n=1,352; chronic MDD subsample: n=225; controls: n= 1,649). The 1,000 Genomes database was used as reference for imputation. From 157 studies identified inthe literature, 81 studies reported significant associations with MDD, involving 245 polymorphisms in 97 candidate genes, from which we were able to investigate 185 SNPs in 89 genes. We replicated nine candidate SNPs in eight genes for MDD and six in five genes for chronic MDD. However, these were not more than expected by chance. At gene level, we replicated 18 genes for MDD and 17 genes for chronic MDD, both significantly more than expected by chance. We showed that replication rates were improved for MDD compared to a previous, highly similar, replication study based on studies published before 2007. Effect sizes of the SNPs and replication rates of the candidate genes were improved in the chronic subsample compared to the full sample. Nonetheless, replication rates were still poor.
Full-text Article · Nov 2015 · American Journal of Medical Genetics Part B Neuropsychiatric Genetics
[Show abstract][Hide abstract]ABSTRACT: The literature on relative age position effects is rather inconsistent. In this study we examined intra-classroom age position (or relative age) effects on Dutch adolescents' school progress and performance (as rated by teachers), physical development, temperamental development (fear and frustration), and depressive symptoms, all adjusted for age at the time of measurement. Data were derived from three waves of Tracking Adolescents' Individuals Lives Survey (TRAILS) of 2230 Dutch adolescents (baseline mean age 11.1, SD = 0.6, 51% girls). Albeit relative age predicted school progress (grade retention ORs = 0.83 for each month, skipped grade OR = 1.47, both p<.001), our key observation is the absence of substantial developmental differences as a result of relative age position in Dutch adolescents with a normative school trajectory, in contrast to most literature. For adolescents who had repeated a grade inverse relative age effects were observed, in terms of physical development and school performance, as well as on depressive symptoms, favoring the relatively young. Cross-cultural differences in relative age effect may be partly explained by the decision threshold for grade retention.
[Show abstract][Hide abstract]ABSTRACT: Although it has often been suggested that physical activity and depression are intertwined, only few studies have investigated whether specific aspects of physical activity predict the incidence of major depression in adolescents from the general population. Therefore the aim of this study was to investigate the effects of nature, frequency, duration and intensity of physical activity during early adolescence on the onset of a major depressive episode in early adulthood. In a population sample of adolescents (N = 1396), various aspects of physical activity were assessed at early adolescence (mean age 13.02, SD = 0.61). Major depressive episode onset was assessed using the Composite International Diagnostic Interview. A Cox regression model was performed to investigate whether physical activity characteristics and their interactions with gender predicted a major depressive episode onset up until mean age 18.5 (SD = 0.61). The individual characteristics of physical activity (nature, frequency, duration and intensity) or their interactions with gender did not predict a major depressive episode onset (p values >0.05). So far, there is no prospective evidence that physical activity protects against the development of adolescent depressive episodes in either boys or girls.
Full-text Article · Jun 2013 · Journal of Psychiatric Research
[Show abstract][Hide abstract]ABSTRACT: Objective:
Physical activity is inversely associated with depression in adolescents, but the overall associations are fairly weak, suggesting individual differences in the strength of the associations. The aim of this study was to investigate whether plasticity genes modify the reciprocal prospective associations between physical activity and depressive symptoms found previously.
In a prospective population-based study (N = 1,196), physical activity and depressive symptoms were assessed three times, around the ages of 11, 13.5, and 16. Structural Equation Modeling was used to examine reciprocal effects of physical activity and depressive symptoms over time. The plasticity genes examined were 5-HTTLPR, DRD2, DRD4, MAOA, TPH1, 5-HTR2A, COMT, and BDNF. A cumulative gene plasticity index consisting of three groups (low, intermediate, and high) according to the number of plasticity alleles carried by the adolescents was created. Using a multigroup approach, we examined whether the associations between physical activity and depressive symptoms differed between the three cumulative plasticity groups, as well as between the individual polymorphisms.
We found significant cross-sectional and cross-lagged paths from physical activity to depressive symptoms and vice versa. Neither the cumulative plasticity index nor the individual polymorphisms modified the strengths of these associations.
Associations between adolescents' physical activity and depressive symptoms are not modified by plasticity genes.
[Show abstract][Hide abstract]ABSTRACT: Low levels of physical activity (PA) have been shown to be associated with depression in adults. The few studies that focused on adolescents yielded mixed and inconsistent results. Efforts to examine the direction of this relationship have been inconclusive up to now. The aims of this study were therefore to investigate (1) the direction of the inverse association between PA and depressive symptoms over time, and (2) whether these associations are specific to particular clusters of depressive symptoms in adolescents.
Depressive symptoms and PA were assessed in a population sample of adolescents (N = 2,230) who were measured at three waves between age 10 and age 17. Depressive symptoms were measured by the Affective Problems scale of the Youth Self-Report and Child Behavior Checklist, whereas PA was operationalized as the amount of time spent on physical exercise. Structural equation modeling was used to examine bidirectional effects of PA and depressive symptoms over time.
We found significant cross-lagged paths from prior PA to later depression as well as from prior depression to later PA (beta values = -.039 to -.047). After subdividing depression into affective and somatic symptoms, the affective symptoms were reciprocally related to PA, whereas the paths between somatic symptoms and PA did not reach statistical significance.
An inverse bidirectional association between PA and general depressive symptoms was observed. This association was restricted to affective symptoms.
Full-text Article · May 2012 · Journal of Adolescent Health