Infections and Adult Schizophrenia

We reported previously that residents of Greater Helsinki, Finland, whose mothers were ex-posed to the 1957 influenza epidemic during their second tri-mester of gestation had a signifi-cantly elevated risk of develop-ing adult schizophrenia. The majority of the replication stud-ies to date have not determined whether the mothers actually contracted an infection or the stage of gestation based on mother's last menstruation. We read prenatal clinic records of the mothers of the Helsinki-born schizophrenia subjects to deter-mine timing of infection, as noted by the prenatal clinic obstetric nurse at a time close to the actual infection. Schizophre-nia subjects who were exposed in the second trimester had a significantly higher rate of defi-nite influenza infection (86.7%) in that period compared to those who were exposed during the first and third trimesters (20.0%). These results are interpreted with caution because of the small number of cases