Influenza during 2nd Trimester of Pregnancy Linked to 300% increase in risk of Schizophrenia and Affective Disorder

Pregnant women who are not vaccinated against the flu could be putting their unborn babies at risk of brain damage, schizophrenia and developmental problems.

A study of more than 6000 children, by American and Finnish researchers, found that the children of mothers who suffered influenza in the last six months of pregnancy were more likely to experience problems, such as schizophrenia, attention deficit hyperactivity disorder and depression.

Additionally, in a separate report in the 1997 Archives of General Psychiatry, Dr. Ricardo A. Machon of Loyola Marymount University in Los Angeles and a multinational team evaluated a group of adults who had been exposed in-utero to the 1957 influenza epidemic in Helsinki, Finland.

In an earlier study, these same researchers found a higher than expected incidence of schizophrenia in these subjects. Since adult affective disorder, like schizophrenia, has been proposed to have a neurodevelopmental origin, Dr. Machon and colleagues revisited their original data to look for an association between influenza exposure and major affective disorder.

The incidence of major affective disorders in the exposed cohort was significantly higher than in controls, 13% versus 2%. The significance of this relationship remained when population-based estimates were used. In addition, the influenza exposure effect appeared to be slightly stronger in men, "...although the rates of major affective disorder in women were similar."

The findings "...provide suggestive evidence for a neurodevelopmental genesis for a subgroup of major affective disorders in the second trimester," Dr. Machon explains. He adds, "It is conceivable that second-trimester neural developmental disturbance is associated with an increased likelihood of delusional symptomatology and absence of formal thought disorder and that the decompensation may take the form of schizophrenia or major affective disorder."

In a recent interview with a leading researcher in this area, it was stated ""Perhaps physicians will use this information to caution women to avoid situations which might put them at risk for viral infections if at all possible," said Dombrowski. "In addition, it might be advisable for women who will be in the second or third trimester of pregnancy during flu season to obtain a flu vaccine."

From Research reports in 2003 and 1997 - Arch Gen Psychiatry 1997;54:322-328.