What causes the scrambling of mind that characterizes
schizophrenia? At alecture given in the spring of 1993 at Harvard Medical
School, Daniel Weinberger, M.D., chief of the National Institute of
Mental Health's Brain Disorder Branch, spoke of the latest findings. "We
don't have a smoking gun yet," he admitted, "but we have a gun that is
threatening to smoke."
Many researchers have identified differences in the brains of
schizophrenics compared to non-schizophrenics. A few years ago, Dr.
Torrey was one of the first to use magnetic resonance imaging to show
that the fluid-filled ventricles in the brains of schizophrenics are
larger than those of their non-schizophrenic twins. More recently,
researchers at the University of California at Irvine found, in a
post-mortem study of seven schizophrenics, that most of the neural cells
that should have migrated during the second trimester of pregnancy to
higher brain regions, the hippocampus and neocortex, never made it out of
lower brain areas such as the white matter of the temporal and frontal
lobe.
Then, in August of 1992, The New England Journal of Medicine
published a major study linking a specific symptom of schizophrenia with
specific changes in the brain. Harvard University researchers found that
the jumbled and disordered thinking of schizophrenia was associated with
brain-size reductions of up to 19 percent in regions of the temporal lobe
crucial to speech and language. The more disordered the thinking, the
smaller the regions. "This is one of the first times that a relationship
has been found between specific clinical symptoms of schizophrenia and
brain reduction i a specific area," said Althea Wagma, Ph.D., chief of
the NIMH Schizophrenia Research Branch's neuroimaging the
electrophysiology research program. "This may have significant
implications for how we ought to design future studies, to ask questions
about the relationship between brain dysfunction and behavioral
dysfunction."
Genes almost surely play a role in these changes: a recent study in
the British journal Nature reported the presence of repeated segments of
the gene that codes for the dopamine receptor protein on the surface of
brain cells. And since excess amounts of the neurotransmitter dopamine
have been shown to be associated with schizophrenia, researchers believe
that the genetic mutation may be the cause, by preventing brain cells
from properly absorbing dopamine.
Many other studies of inheritance patterns have also suggested a
genetic link. Most recently, Josef Parnas, M.D., of Copenhagen University
published a study showing that 16 percent of the children of
schizophrenic mothers grow up to be schizophrenic themselves--compared to
just 1.9 percent of the children of non-schizophrenic mothers.
Yet genes are clearly not the only cause.
Other studies have shown that higher rates of schizophrenia occur
in offspring whose birth was marked by obstetric complications and in
those born to mothers who caught the flu during the fifth month of
pregnancy.
Other environmental causes have also been suggested: a 14-year-old
study of 49,000 young Swedish men by Glyn Lewis, M.D., of London's
Institute of Psychiatry found that those who had grown up in cities were
65 percent more likely to develop schizophrenia than those who had been
raised in rural areas. In perfect dose-response fashion, those reared in
large towns had a risk midway between that of city reared and country
reared.
Although Lewis noted that viral illnesses and head injuries are
both more common in cities, it could also be the stress of urban life
that contributes to the risk of developing schizophrenia. Indeed, other
studies have found that in the U.S., the states with the greatest
proportion of people living in cities (particularly in the Northeast)
have about twice the rate of schizophrenia as those with the fewest.
Worldwide, the disease appears to be far more common in westernized
countries than in Third World countries. Historically, too, some
researchers believe that schizophrenia has become increasingly prevalent
in the past 200 years, with the rise of urbanization.
ILLUSTRATION
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daniel weinberger,
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institute of mental health,
magnetic resonance imaging,
national institute of mental health,
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new england journal,
new england journal of medicine,
schizophrenia,
schizophrenia research,
second trimester of pregnancy,
size reductions,
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trimester of pregnancy,
university of california at irvine,
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