METHOD: Genome-wide association studies (GWASs) were conducted in Australian (between 1988 and 1990 and between 2010 and 2013) and Amish (between May 2010 and December 2011) samples in whom the Seasonal Pattern Assessment Questionnaire (SPAQ) had been administered, and the results were meta-analyzed in a total sample of 4,156 individuals. Genetic risk scores based on results from prior large GWAS studies of bipolar disorder, major depressive disorder (MDD), and schizophrenia were calculated to test for overlap in risk between psychiatric disorders and seasonality.
RESULTS: The most significant association was with rs11825064 (P = 1.7 × 10⁻⁶, β = 0.64, standard error = 0.13), an intergenic single nucleotide polymorphism (SNP) found on chromosome 11. The evidence for overlap in risk factors was strongest for schizophrenia and seasonality, with the schizophrenia genetic profile scores explaining 3% of the variance in log-transformed global seasonality scores. Bipolar disorder genetic profile scores were also associated with seasonality, although at much weaker levels (minimum P value = 3.4 × 10⁻³), and no evidence for overlap in risk was detected between MDD and seasonality.
CONCLUSIONS: Common SNPs of large effect most likely do not exist for seasonality in the populations examined. As expected, there were overlapping genetic risk factors for bipolar disorder (but not MDD) with seasonality. Unexpectedly, the risk for schizophrenia and seasonality had the largest overlap, an unprecedented finding that requires replication in other populations and has potential clinical implications considering overlapping cognitive deficits in seasonal affective disorders and schizophrenia.
METHODS: A cross-sectional study was carried out in the district of Johor Bahru, Malaysia. Of the 1,200 women approached from membership of community associations, 1,002 (84%) completed the questionnaires. Severe life events Recent Life Events Questionnaire (Brugha and Cragg in Acta Psychiatr Scand 82:77-81, 1990) and psychosocial vulnerability (VDQ) (Moran et al. in Br J Clin Psychol 40:411-427, 2001) were used to measure vulnerability factors. Depression was measured by the General Health Questionnaire (GHQ-30) (Havenaar et al. in Soc Psychiatry Psychiatr Epidemiol 43:209-215, 2008).
RESULTS: Single mothers had significantly higher rates of depression than those married (60.5 vs. 39.5%), as well as higher rates of severe life events and Negative Elements in Close Relationships (lack of support and conflict with children). However, married mothers had greater Negative Evaluation of Self. The two vulnerability factors were correlated to each other and to severe life events and social adversity. Logistic regression showed an interaction between severe life events in the material and relationship domains and joint vulnerability for depression outcome. The results are discussed in relation to the low recognition of psychosocial risks for depression in single mothers in Malaysia, as well as lack of appropriate services.