Maternal influenza in the etiology of schizophrenia.

There are epidemiological reasons for suspecting that infections may contribute to the etiology of schizophrenia, and it is claimed that the birth cohort that was in utero during the 1957 influenza epidemic in Helsinki, Finland, now has an increased incidence of schizophrenia. Three studies, all based on the admission statistics of Scottish psychiatric hospitals, were therefore undertaken to determine whether those who were in utero during the influenza A epidemics of 1918 to 1919 and 1957 were subsequently at increased risk of schizophrenia. Edinburgh data suggest that those who were in the sixth month of intrauterine development during the 1957 epidemic were subsequently at increased risk, but Scottish national data do not reveal any increased risk associated with either the 1918 to 1919 or 1957 epidemics. Overall, the hypothesis that maternal influenza may contribute to the etiology of schizophrenia is not supported, but the possibility cannot yet be discounted.