Seasonal variation in depressive disorders and suicidal deaths in New South Wales.

Month of admission data to psychiatric facilities in New South Wales, 1971-76, were examined for some 23,000 patients with a depressive disorder to determine if seasonal variations in admissions, described in the northern hemisphere, exist there. In addition, data were examined on month of occurrence of some 3,000 deaths due to suicide and self-inflicted injury, over the same period. Seasonality was demonstrated for three 'psychotic' depressive disorders, but not found for neurotic depression, further supporting the binary view of depression. A peak incidence in spring was found for MDP-mania and reactive depressive psychosis, while the peak incidence for MDP-depression was was in late winter. It is suggested that the increase in certain affective disorders around spring may follow a rapid increase in luminance, and in stimulation of the pineal gland. Suicidal deaths of males did not show significant seasonality, while those of females showed two incidence peaks, the significant one occurring in spring.