Seasonality of admissions in the psychoses: effect of diagnosis, sex, and age at onset.

A summer peak was found in first admissions to hospitals in England and Wales between 1976 and 1986 for both affective psychoses and schizophrenia, but not for neurotic conditions or personality disorders. There was no significant relationship between age at first admission and season of admission. The summer peak was most prominent for mania, where it was present in both sexes; for schizophrenia, it was present only in females. These findings suggest that schizophrenia in females, and mania in both sexes, have some aetiological or precipitating factor in common.