A relation between seasonal temperature and the birth rate of schizophrenic patients.

The relation between schizophrenia birth rates and environmental temperature was studied in patients born in England and Wales during 1921-1955 and first admitted there in 1970-1977. A methodological difficulty due to varying age-incidence was avoided by the use of indices independent of yearly changes in rates. Birth rates in the second quarter and in the first half of the year showed high negative correlations with mean temperatures of the first quarter and first half of the year. Comparison of years with the coldest and with the warmest seasons showed the schizophrenia birth rate to be consistently higher in the coldest years. No comparable relations between birth rates and temperature were found for patients with affective psychosis, neurosis or personality disorder. The findings indicate an association between schizophrenia birth rates and temperature of a kind similar to that between infant death rates and temperature during the years 1921-55. Some implications are discussed.