SEASON OF BIRTH AND SCHIZOPHRENIA - SEX DIFFERENCE

1. A statistically significant increased risk of schizophrenia for ind ividuals born in winter has been reported. The increase risk is of the order of 5-15%. The seasonal effect is more marked among females. Thi s winter birth effect suggests some environmental agents, probably a n europathogen one, acting on the foetus. 2. The present study sought to test the environmental damage hypothesis by application of the family history of psychiatric disorder distinction to season of birth data d ivided according to sex and using a control population. 3. From comput er records, all patients admitted to the psychiatric department of Mar seilles Timone hospital between January 1984 and December 1989 who sat isfied DSM III, DSM III R criteria for schizophrenia were identified. Patients were then classified into two groups : family history of psyc hiatric disorder versus no family history. Division according to the s ex was carried on after two groups were formed. 4. The data show (1) a significant excess of births in the early months of the year (p < 0.0 5) for all patients with no family history of psychiatric disorder, (2 ) a significant excess of births for females (p < 0.05) with no family history. 5. These results provide indirect support for the neurodevel opmental theory of schizophrenia.