PhotoThe children of pregnant women exposed to the flu have four times the risk of developing bipolar disorder in adulthood, according to a new study funded by the National Institutes of Health.  

The findings add to mounting evidence of possible shared underlying causes and illness processes with schizophrenia, which some studies have also linked to prenatal exposure to influenza. Similar processes may influence develop of autism, some researchers think.

“Prospective mothers should take common sense preventive measures, such as getting flu shots prior to and in the early stages of pregnancy and avoiding contact with people who are symptomatic,” said Alan Brown, M.D., M.P.H, of Columbia University and New York State Psychiatric Institute.

Flu shots are best prevention

“In spite of public health recommendations, only a relatively small fraction of such women get immunized. The weight of evidence now suggests that benefits of the vaccine likely outweigh any possible risk to the mother or newborn,” Brown said. He and colleagues reported their findings online May 8, 2013 in JAMA Psychiatry.

Although there have been hints of a maternal influenza/bipolar disorder connection, the new study is the first to follow families in the same HMO, using physician-based diagnoses and structured standardized psychiatric measures.

Among nearly a third of all children born in a northern California county during 1959-1966, researchers followed 92 who developed bipolar disorder, comparing rates of maternal flu diagnoses during pregnancy with 722 matched controls.

The nearly fourfold increased risk implicated influenza infection at any time during pregnancy, but there was evidence suggesting slightly higher risk if the flu occurred during the second or third trimesters. 

Schizophrenia link

A previous study, by Brown and colleagues, in a related northern California sample, found a threefold increased risk for schizophrenia associated with maternal influenza during the first half of pregnancy.

Autism has also been linked to first trimester maternal viral infections and to possibly related increases in inflammatory molecules.

“Future research might investigate whether this same environmental risk factor might give rise to different disorders, depending on how the timing of the prenatal insult affects the developing fetal brain,” suggested Brown.

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