Prenatal exposure to the 1957 influenza epidemic and adult schizophrenia: A follow-up study

Abstract

Background. We investigated the hypothesis that prenatal exposure to the 1957 A2 influenza increases the risk of schizophrenia in adulthood. Method. We traced a cohort of individuals known to have been exposed to the 1957 influenza epidemic during gestation and an unexposed cohort matched for period of gestation and hospital of birth. Follow-up information on psychiatric illness in subjects was sought from two sources: maternal interview and psychiatric hospital admission data. Results. Follow-up information was obtained on 54% of the sample: 238 subjects from the influenza-exposed group and 287 subjects from the unexposed group. There was no increased risk of schizophrenia among the exposed cohort compared to the unexposed cohort (relative risk 1.1; 95% CI 0.41-2.95), although there was an increase in depressive illness (relative risk 1.59; 95% CI 1.15-2.19). Conclusions. The association between prenatal influenza and an increased risk of schizophrenia in adulthood has thus far been found only in population based data and is not supported by the present observational study which has information about exposure and outcome in individuals.