Pregnant mothers exposure to the flu was associated with a nearly fourfold increased risk that their child would develop bipolar disorder in adulthood, according to results of a 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 also have linked to prenatal exposure to influenza, according to a NIH news release.
“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,” Alan Brown, MD, MPH, of Columbia University and New York State Psychiatric Institute, and a grantee of the NIHs National Institute of Mental Health, said in a news release.
“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.”
Although there have been hints of a connection between maternal influenza and bipolar disorder, the new study, published May 8 on the website of JAMA Psychiatry, is described as the first to prospectively follow families in the same HMO, using physician-based diagnoses and structured, standardized psychiatric measures.
Access to unique Kaiser Permanente, county and Child Health and Development Study databases made possible the inclusion of more cases with detailed maternal flu exposure information than in previous studies, according to the news release.
Among nearly a third of all children born in a Northern California county between 1959 and 1966, researchers followed 92 who developed bipolar disorder, comparing rates of maternal flu diagnoses during pregnancy with 722 matched controls.
The nearly quadruple 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.
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 been similarly 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,” Brown said.
Bipolar disorder and schizophrenia share a number of other suspected causes and illness features, the researchers noted. For example, both share early-adulthood onset of symptoms and susceptibility genes, run in the same families, affect nearly 1% of the population, show psychotic behaviors and respond to antipsychotic medications.
Increasing evidence of such overlap between traditional diagnostic categories has led to the NIMH Research Domain Criteria project, which is laying the foundation for a new mental disorders classification system based on brain circuits and dimensional mechanisms that cut across traditional diagnostic categories.
Read the study abstract: http://archpsyc.jamanetwork.com/article.aspx?articleid=1686037.