Bipolar disorder can be debilitating for sufferers, causing severe shifts in mood that can result in damaged relationships, poor performance at school or work, hospitalization and even suicide.
A new study finds a risk factor for the mental health disorder may be having a mother who had the flu when she was pregnant. The authors are calling for future studies to confirm this link. If confirmed, they hope to discover what about the flu virus may trigger the disorder.
"These findings may have implications for prevention and identification of pathogenic mechanisms that lead to" bipolar disorder, concluded the researchers, led by Dr. Alan Brown, a professor of clinical psychiatry and epidemiology at Columbia University Medical Center in New York City.
Researchers studied a pool of more than 900 U.S. children. More than 200 had been enrolled in the Child Health and Development Study, which tracked kids born between 1950 and 1966. The remaining 700 participants were controls matched by age and gender, obtained from county health databases.
The researchers found 92 cases of bipolar disorder out of the entire participant pool. After combing through data, their analysis revealed having flu during pregnancy was tied to a four-fold risk increase that offspring would develop bipolar disorder by the time they became adults.
The study was published May 8 in JAMA Psychiatry.
Bipolar disorder is characterized by ups and downs that are more extreme than a person typically experiences. It often develops in a person in their late teens or early 20s, though some people may experience symptoms in childhood, notes the National Institute of Mental Health.
People may experience unusually intense emotional states that occur during "mood episodes." A euphoric, overexcited state is called a manic episode, and an extremely sad or hopeless state is called a depressive episode. The disorder usually lasts a lifetime, with episodes of mania and depression typically returning back over time.
Should women thinking about having children be worried?
"The chances [of developing bipolar disorder] are still quite small," Brown told the BBC. "I don't think it should raise alarms for mothers."
His study did not look at what about the virus may cause this disorder to appear in children as they age.
"We don't fully understand this," Brown told HealthDay. "The best guess is it's an inflammatory response. It could also be a result of feve."
He recommended pregnant women get a vaccine to reduce their risk of getting the flu.
The Centers for Disease Control and Prevention recommends all pregnant women get a flu shot, calling it a safe way to protect a mother and her unborn child from serious illness and complications from influenza.
Brown's team previously found increased risk for schizophrenia among offspring of women who had the flu when pregnant.
A study published in Pediatrics last November found flu during pregnancy raised risk a child may develop autism. The study authors at the time cautioned it was too soon for their findings to cause concern among prospective mothers.
"It certainly adds to the growing body of evidence that some problems of early neurodevelopment are related to infection exposure in pregnancy," Dr. Robert Yolken, a professor of pediatrics at Johns Hopkins Children's Health Center in Baltimore, told Medscape.