Schizophrenia Linked to Flu During Pregnancy
Risk of Schizophrenia Rises With Flu Exposure in First Trimester, Study Suggests
Aug. 2, 2004 -- Babies whose mothers are exposed to the flu
virus during pregnancy may face a higher risk of developing schizophrenia in
later life, a new study suggests.
Although many previous studies have linked prenatal exposure to
influenza with adult schizophrenia, researchers say this is the first study
based on laboratory evidence of flu exposure during pregnancy.
The study showed that the risk of schizophrenia was three times
higher among adult children exposed to influenza during the first half of
pregnancy compared with those who had not been exposed. But there was no
increase in risk associated with influenza exposure during the second half of
"These findings represent the strongest evidence thus far
that prenatal exposure to influenza plays a role in schizophrenia," says
researcher Ezra Susser, MD, DrPH, chairman of the department of epidemiology at
the Mailman School of Public Health at Columbia University, in a news release.
"Although the findings may ultimately have implications for prevention, we
strongly caution against making any public health policy recommendations until
these links have been confirmed through further study."
Schizophrenia is a severe mental disorder that affects about 1%
of the population. The exact cause is unknown, but it's likely caused by a
combination of factors such as heredity, problems in the way the brain develops
before birth, and problems experienced during pregnancy that may affect the
development of the baby's nervous system, including exposure to a virus.
New Evidence of Influenza-Schizophrenia Link
In the study, which appears in the August issue of the
Archives of General Psychiatry, researchers followed a large group of
children born to mothers in Alameda County, Calif., who were part of the Child
Health and Development Study from 1959-1966. The children were followed up for
psychiatric disorders 30-38 years later.
Researchers identified 64 of the adult children as having
schizophrenia and compared them to 125 similar, healthy study participants.
The study showed that the risk of developing schizophrenia was
seven times higher among those children whose mothers were exposed to influenza
during the first trimester of pregnancy based on blood tests.
There was no increased risk of schizophrenia associated with
influenza exposure during the second or third trimester.
When researchers looked at a broader time period of influenza
exposure during pregnancy, they found the risk of schizophrenia was about three
times higher for those exposed during early to mid-pregnancy.
"Our data suggest the possibility that up to 14% of
schizophrenia cases would not have occurred if influenza exposure during early
to midpregnancy had been prevented," write the researchers.
Routine vaccination of nonpregnant women for the flu virus may
be worth considering, the researchers write.