Findings Link Fetal Trauma, Schizophrenia
Strong new evidence supporting the emerging consensus that many cases of schizophrenia are caused by a virus or other trauma that strikes the fetus during the second trimester of pregnancy was reported Wednesday by an Arkansas neurologist.
A growing number of neurologists now are confident that schizophrenia, which affects as many as 2.5 million Americans, is caused by congenital abnormalities in the areas of the brain that control thought and perception. But it has not been clear whether those abnormalities are inherited or caused by something in the environment.
The new evidence gives strong support to the latter possibility, indicating that the disorder is at least partially triggered by a problem in the fetal environment in the womb, such as a lack of oxygen or a viral exposure. Nevertheless, many researchers believe there is a genetic susceptibility to the disorder.
Arkansas neurologist H. Stefan Bracha studied the hands of 24 pairs of identical twins in which only one of the twins suffered from schizophrenia. That only one member of each set of genetically identical twins was schizophrenic is itself strong evidence that a genetic defect was not the primary cause of the disorder in these cases.
But he went further, looking for signs that the fetuses were damaged in the womb, thereby suggesting an environmental cause.
Bracha reported at the Society for Neuroscience meeting in New Orleans that each of the schizophrenic twins had a number of small deformities in their hands, while the unaffected twins did not.
Hands are formed during the second trimester, when crucial brain connections are also forming. The discovery of hand abnormalities indicates that the affected twin suffered some type of trauma, such as a viral infection, and that trauma is likely to have affected the twin’s brain as well, Bracha said.
“This is a brand new approach to asking questions about pre-birth development,” said psychologist Althea Wagman of the National Institute of Mental Health. Bracha’s results, she said, represent “the first time . . . this theory of second-trimester insult might be panning out.”
Bracha thinks the results may have strong implications for prenatal care.
While physicians stress the importance of abstaining from alcohol and medication throughout pregnancy, they usually emphasize the first trimester, Bracha said. “Now we know that the second trimester is at least as important as the first, because that’s when the brain of your child develops.”
Schizophrenia afflicts about 1% of the population. It is characterized by inappropriate emotions, hallucinations and disordered thought processes that cause difficulties in communication, interpersonal relationships and distinguishing between the real and the imagined. It is commonly confused with split or multiple personalities.
The National Institute of Mental Health says that schizophrenia is “the most costly and devastating” mental illness in terms of human suffering. The National Academy of Sciences has said it costs the U.S. economy as much as $48 billion per year.
Many epidemiological studies have shown that a mother’s exposure to the influenza virus during the second trimester greatly increases the risk of the fetus developing schizophrenia as an adult. But that evidence is only suggestive, and researchers have been looking for a more direct link.
Bracha reasoned that a viral infection or some other trauma that affected the brain during the second trimester should produce effects elsewhere in the body as well. But because of variations among individuals, the only sure way to search for such effects was to study twins.
The hand seemed a good possibility because it is formed during the same time as brain circuits are constructed and because it is readily accessible. “A good photograph of the hand can be obtained for study even if the patient is violently ill,” he said.
Other researchers were skeptical about his idea. It took him many years to obtain funding for the project and another seven years to locate the 24 sets of twins.
Bracha found sharp but subtle differences between the twins. The thumb and index finger of each hand, for example, were shorter than those of the other twin. “The difference was really striking to the trained eye,” he said in a telephone interview.
Perhaps more important were differences in fingerprints. Identical twins normally have identical fingerprints, but Bracha found that the affected twins had far fewer ridges in their fingerprints. While a healthy twin might have 200 ridges on 10 fingers, he said, the affected twin might have only 130.
Wagman emphasized that Bracha’s results do not mean that a defect in the fingers is the cause of schizophrenia. Rather, the finding represents “an indirect way of getting at the maldevelopment that occurred during this period,” she said.
“It’s clear,” Bracha said, “that one twin had a perfect internatal life and the other had a poor internatal life. If you talk to obstetricians, you will find out that is not uncommon.”
Bracha believes that two strong conclusion can be drawn from his work. One is that “schizophrenia is an accident of nature, and there should be no stigma attached to it.” The second is the importance of prenatal care.
