For the study, researchers at Columbia University and Kaiser Permanente identified cases of bipolar disorder by database linkages of a Northern California health plan and a county health care system, along with data from a mailed survey.
Participants were mothers who gave birth between 1959 and 1966 and their offspring. Researchers found 92 cases of bipolar disorder and compared them with 722 people matched in terms of occurrence of maternal influenza during pregnancy.
While the new study found an association of pregnant women getting the flu and a higher risk of bipolar disorder in their offspring, it didn't establish a cause-and-effect relationship.
"There is no understanding of the causal factors of this," said Dr. Alan Manevitz, a clinical psychiatrist at Lenox Hill Hospital in New York City. He was not involved with the study.
"Pregnancy itself puts extra stress on women in general," he pointed out. "Pregnancy also affects the immune system and increases the risk of getting the flu."
Flu during pregnancy increases the risk of miscarriage, premature birth and low birth weight infants, Manevitz said.
Pregnant women should get a flu shot, both Manevitz and Brown suggested.
Other studies have shown a similar association between flu during pregnancy and the child's risk for autism and schizophrenia -- now there is this association with bipolar disorder, Manevitz said. "This doesn't give us any causal connection," he emphasized.
To learn more about bipolar disorder, visit the U.S. National Institute of Mental Health.
SOURCES: Alan Brown, M.D., M.P.H., professor of clinical psychiatry and clinical epidemiology, College of Physicians and Surgeons, Columbia University, New York City; Alan Manevitz, M.D., clinical psychiatrist, Lenox Hill Hospital, New York City;
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