Prenatal exposure to influenza as a risk factor for adult schizophrenia.

Objective: Several, but not all epidemiological studies, have demonstrated a positive correlation between exposure to the virus during the second trimester of pregnancy and an increased risk to the infants for subsequently developing schizophrenia. The present study is the first be designed in France to examine the risk of gestational exposure to the influenza virus and subsequent development of schizophrenia.

Method: A total of 974 adults with schizophrenia born between 1949 and 1981 were compared for risk of exposure to influenza with their non-schizophrenic siblings and with matched control patients.

Results: Significantly more schizophrenic subjects than controls (both groups) had been exposed to the influenza virus during the fifth month of pregnancy (OR=2.24, CI: 1.49-3.35, and OR=1.61, CI: 1.04-2.49).

Conclusion: These results suggest that influenza infection during pregnancy is a neurodevelopmental risk factor for schizophrenia in adult life.