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 yesterday 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 were 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 that 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 Dr. Bracha went further, looking for signs that the fetuses were damaged in the womb, which would suggest an environmental cause.
Dr. Bracha reported at the Society for Neuroscience meeting in New Orleans that the schizophrenic twins each had a number of small deformities in their hands, while the unaffected twins did not.
Hands are formed during the second trimester, at the same time that crucial brain connections are being formed. The discovery of hand abnormalities indicates that the affected twin suffered some type of trauma, such as a viral infection, and that trauma was likely to have affected the twin's brain as well, Dr. Bracha said.
"This is a brand-new approach to asking questions about prebirth development," said psychologist Althea Wagman of the National Institute of Mental Health.
Dr. Bracha's results, she said, represent "the first time that . . . this theory of second-trimester insult might be panning out."
Dr. Bracha believes that 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, Dr. 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 percent 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.