Brain Abnormalities Found in Schizophrenics : Medicine: Scientists studying twins have come up with results that suggest environmental factors may be as important as genetics in developing the disease.
Government scientists studying identical twins have found physical abnormalities in specific areas of the brains of victims of schizophrenia, a discovery that should eventually lead to the development of new therapy for the estimated 50% of victims of this disabling mental illness who cannot now be adequately treated with drugs.
Studying pairs of twins in which only one had the mental disorder, researchers from the National Institute of Mental Health report today in the New England Journal of Medicine that the afflicted twin in virtually all cases had a slightly smaller brain in certain key areas, suggesting a non-genetic abnormality in growth of the brain during development.
Researchers have long known that genetics play a key role in the development of schizophrenia, and assumed that environmental factors, such as exposure to a virus during fetal development, played a lesser role. The new results suggest that such factors may be as important as genetics.
“This is a landmark study,” said Dr. Lewis L. Judd, NIMH director, “because previous efforts to link brain abnormalities to schizophrenia have been clouded by the difficulty of interpreting normal variations in individual brain structures. Only by comparing the brains of twins who . . . would be expected to have identical brain structures could NIMH researchers show that the twins with schizophrenia consistently had brain abnormalities not present in their healthy identical twins.”
Because the abnormally small brain segments were found in virtually all twins studied, researchers assume that the finding will hold true for most schizophrenics. If so, that would constitute one of the few unifying features of this enigmatic disease.
Schizophrenia afflicts, or will afflict, about 1% of the population, an estimated 2.5 million Americans. 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, but that is an entirely different class of disorder.
“While schizophrenia is by no means the most common mental illness,” according to an NIMH report, “it is probably the most costly and devastating in terms of human suffering.” NIMH has estimated the annual cost of schizophrenia to the U.S. economy as $21 billion, while the National Academy of Sciences has said that it costs society as much as $48 billion a year.
Many researchers have reported finding evidence of structural abnormalities in the brains of schizophrenics, such as a smaller hippocampus, which is involved in thinking and perception, but interpretation of these studies has been difficult because of the large variability in brain size from individual to individual. A given “abnormality” might thus be found in only a third to a half of patients studied, leaving open many questions about its role in the disease.
The new findings by neurologist Daniel R. Weinberger and his colleagues at NIMH’s St. Elizabeths Hospital in Washington should answer those questions. These findings, along with a previous study by psychiatrist Michael Reveley of London Hospital in the United Kingdom, provide “nearly definitive evidence” of the existence of structural abnormalities in the disease.
Reveley and his colleagues reported in 1982 on computed tomography (CT) scanning of 12 sets of identical twins. CT uses X-rays to image cross-sections of the brain. In 11 of the 12 pairs, they found that the affected twin had larger ventricles, fluid-filled cavities in the brain. By inference, if the ventricles were larger than normal, the brain tissue must have been smaller than normal.
But the CT scans did not have high enough resolution to show which parts of the brain were smaller.
Weinberger and his colleagues used a newer technique called magnetic resonance imaging, which provides a much more detailed picture of the brain. “It’s like holding a brain in your hand,” he said in a telephone interview.
They studied 15 pairs of twins, eight male and seven female, with an age range of 25 to 44 years. They found that, compared to the normal twins, the left hippocampus was significantly smaller in 14 of the schizophrenic twins and the right hippocampus was smaller in 13. The schizophrenic twins’ temporal lobes were also smaller.
In 12 of the twin pairs, the differences were so large that the afflicted twin could be readily identified just by looking at the images.
Now, Weinberger said, “researchers can focus in on a specific area as consistently abnormal and find out what has happened, what has specifically affected it. . . . Before, if an area was found to be only occasionally abnormal, it wasn’t worth all that much attention.”
Ideally, he said, researchers will be able to find specific biochemical abnormalities in those regions and develop new drugs to force the biochemistry back to normal.
