Schizophrenia risk with flu exposure

Infants exposed to influenza in the womb during the first half of pregnancy appear to have an increased risk of schizophrenia. Researchers from the New York State Psychiatric Institute, evaluated blood samples from women who participated in the prenatal determinants of schizophrenia study to look for evidence of influenza exposure. The study group included pregnant women who received obstetric care from the Kaiser Foundation Health Plan in Alameda County, California, between 1959 and 1966. Among 12,094 children born, sixty-four were diagnosed with schizophrenia, schizo-affective disorder, delusional disorder, psychotic disorder not otherwise specified or schizotypal personality disorder between 1981 and 1997. The study also included 125 children who were matched to the cases for gender, date of birth, and timing of maternal blood draws.

The investigators found a three-fold increased risk of schizophrenia spectrum disorder for those exposed to influenza during the first half of pregnancy. The risk was even higher for those exposed during the first trimester.The antibodies elicited by the virus in the pregnant women can cross the placenta, disturb fetal brain development and increase vulnerability to schizophrenia. Other possible mechanisms include fever in the mother, use of over-the-counter medications or reduced oxygen levels in the fetus.

The researchers suggest that up to 14 per cent of schizophrenia cases would not have occurred if influenza exposure during early to mid-pregnancy had been prevented. Simply vaccinating women of reproductive age against influenza may reduce the rate of schizophrenia in the population.

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