A new study funded by the National Institutes of Health discovers a pregnant mothers’ exposure to the flu may have extreme mental health consequences for the child.
If the mother contracts the flu, the child has a nearly four-fold increased chance of developing bipolar disorder in adulthood, say researchers.
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.
“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.
“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 and colleagues reported their findings online in the journal JAMA Psychiatry.
Although researchers have suspected a linkage between maternal influenza and bipolar disorder, the new study is the first to prospectively follow families using physician-based diagnoses and structured standardized psychiatric measures.
The research was made possible by use of comprehensive electronic medical records by Kaiser-Permanente, in association with county and Child Health and Development Study databases.
This shared health care data repository allowed the evaluation of more cases with detailed maternal flu exposure information than in previous studies.
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.
Moreover, the researchers linked flu exposure to a nearly six-fold increase in a subtype of bipolar disorder with psychotic features.
Prior research suggested a threefold increased risk for schizophrenia associated with maternal influenza during the first half of pregnancy.
Autism has similarly 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.
Bipolar disorder shares with schizophrenia a number of other suspected causes and illness features, the researchers note.
For example, both share onset of symptoms in early adulthood, susceptibility genes, run in the same families, affect nearly one percent of the population, show psychotic behaviors and respond to antipsychotic medications.