Seasonality of birth in seasonal affective disorder

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, 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. The authors compared the observed number of births in their 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), the authors 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).