This study was designed to investigate the possible relationship between completed suicides, depressive disorders, and seasonal variation. All deaths by suicide in North Carolina (N = 3,672) and admissions to the Durham Veterans Administration Hospital Psychiatry Service (N = 3,258) from 1965 to 1971 were tabulated for data analyses. Observed distribution of suicides was not significantly higher for special holidays, weekdays vs weekends, months, or seasons, but was for days of the week (highest on Mondays). Based on discharge diagnoses, the observed distribution of patients admitted with depression was not significantly higher for any month of the year. Further, there was no significant correlation of climatic variables with completed suicides. Results did show a seasonal relationship between suicide and depression. It seems that early recognition and treatment of depression may be the most effective measure for suicide prevention.
Zung WWK, Green RL. Seasonal Variation of Suicide and Depression. Arch Gen Psychiatry. 1974;30(1):89-91. doi:10.1001/archpsyc.1974.01760070067010