Season of birth has no effect on symptoms of depression and anxiety in older adults.

There remains a lack of conclusive evidence as to the merit of season of birth as a predictor of mental illness across contexts. We studied 72,370 individuals (55% women; mean age 66) from the Survey on Health, Ageing and Retirement in Europe. Depressive symptoms were assessed with EURO-D scale and symptoms of anxiety with modified Beck Anxiety Inventory. Multilevel modeling was used to assess the association of season of birth as well as month of birth with symptoms of depression and anxiety, by sex and region. Adjusting for sex and age, month of birth explained only 0.01% to 0.07% of anxiety and depressive symptoms with non-significant improvement in the overall models; using season of birth instead of month of birth added 0.00% to 0.04% of explained variance. When stratified by sex and European region, age explained 0.23% to 5.19% of anxiety and depressive symptoms; the addition of month of birth or season of birth improved the models by negligible amount. Season of birth and month of birth are not reliable predictors of anxiety and depression across the life course.