Seasonality of birth in subtypes of chronic schizophrenia.

Several reports in the literature suggest that schizophrenic patients are disproportionately born during the colder months compared to the general population. In this study, we report differences in the seasonality of birth between the subtypes of chronic schizophrenia, particularly when gender is considered. Cold months' births (December to March) are most likely in nonparanoid females and paranoid males. Possible reasons for these differences are discussed in light of genetic and environmental factors in schizophrenia.