September 1990

Exposure to Influenza Epidemics During Gestation and Adult SchizophreniaA 40-Year Study

Author Affiliations

From the Social Science Research Institute, University of Southern California, Los Angeles (Mr Barr and Dr Mednick); and the Institute of Psychiatric Demography, Psychiatric Hospital I, Aarhus, Denmark (Dr Munk-Jorgensen).

Arch Gen Psychiatry. 1990;47(9):869-874. doi:10.1001/archpsyc.1990.01810210077012

• We attempted to replicate earlier findings of an association between exposure to influenza in the second trimester of gestation and adult schizophrenia. The number of live births, of births of future schizophrenics, and of cases of influenza reported to the Ministry of Health in Denmark was ascertained by month from 1911 to 1950. The relationship between fetal exposure to influenza and adult schizophrenia was examined. It is possible that unknown factors produce excesses of both influenza and schizophrenia in the winter, creating an artifactual association. To control for this coincidence, the effects of season were removed from the monthly influenza and schizophrenic birthrates by several methods. Using the residual scores, it was found that influenza rates higher than seasonally expected, occurring in the sixth month of gestation, were associated with rates of births of schizophrenics greater than seasonally expected. This association was not attributable to some winter-related, third factor or to climatic variables.