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Maternal influenza increased bipolar disorder risk in offspring

Adults have an increased risk for bipolar disorders if their mothers had influenza while pregnant, according to recent study results published in JAMA Psychiatry.

“Although replication is required, the findings suggest that prevention of maternal influenza during pregnancy may reduce the risk of bipolar disorder,” researchers wrote.

The case-control, population-based study included nearly all pregnant women receiving obstetric care from the Kaiser Permanente Medical Care Plan, Northern California Region, from 1959 to 1966. There were 92 confirmed cases of bipolar disorder among 214 study participants and 722 control participants.

Researchers found that adult offspring were nearly four times more likely to have bipolar disorder after exposure to maternal influenza at any time during pregnancy (OR=3.82; 95% CI, 1.58-9.24). Results were not confounded by maternal age, race, educational level, gestational age at birth, and maternal psychiatric disorders.

They also found that when mothers had influenza during their third trimester there was a near fivefold increased risk for bipolar disorder.  

When findings were restricted to bipolar disorder I, they were similar to the categorization of bipolar disorder, according to researchers. Maternal influenza exposure led to a more than fourfold increased risk for bipolar disorder (OR=4.40; 95% CI, 1.77-10.9). Maternal influenza exposure also caused an increased risk for bipolar disorder with psychotic features (OR=5.74; 95% CI, 1.52-21.7).

“If confirmed by studies in other birth cohorts, these findings may have implications for prevention and identification of pathogenic mechanisms that lead to bipolar disorder,” researchers wrote. “Further work, including serologic studies for maternal influenza antibody in archived specimens from this cohort, is warranted.”

Disclosure: The researchers report no relevant financial disclosures.