Schizophrenia is 'umbrella disease' of eight gene disorders, study finds
Study finds debilitating mental illness results from distinct clusters of gene variations, not a single gene
Schizophrenia is not a single disease caused by one gene, but rather a
group of eight distinct genetic disorders — each with its own set of
symptoms, according to a study released Monday.
The new findings, published in The American Journal of Psychiatry, could help doctors diagnose and treat the often-debilitating symptoms associated with the mental illness.
While schizophrenia affects people in different ways, some of the most
common manifestations include hallucinations or delusions, disorganized
speech and behavior, and a disassociation of thoughts and emotions.
Previous research had already led scientists to believe that around
80 percent of the risk of schizophrenia was genetic, but until now they
could not determine where it originated. The study’s findings suggest
that distinct clusters of gene variations — not a single gene — causes
the disease.
“Genes don’t operate by themselves,” C. Robert Cloninger, one of the study’s senior researchers, explained.
“They function in concert much like an orchestra, and to understand how
they’re working, you have to know not just who the members of the
orchestra are, but how they interact.”
Researchers based their conclusions on a gene study of more than
4,000 people with schizophrenia and 3,800 others without the condition.
Individual genes have inconsistent connections to schizophrenia, but
groups of interacting genes were found to contribute to an extremely
high risk of the disease — making it nearly impossible for individuals
with those genetic variations to avoid the illness, the report said.
They found that those specific genetic variations worked together to
produce different severities of the mental illness. People who had
distinct gene clusters — 42 of which were identified in the study
— were between 70 and 100 percent likely to develop schizophrenia,
according to the report.
Of those clusters, researchers were able to identify eight
qualitatively unique disorders within what they now see as the “umbrella
disease” of schizophrenia — each with its own symptoms and level of
severity.
“What we’ve done here, after a decade of frustration in the field of
psychiatric genetics, is identify the way genes interact with each
other, how the ‘orchestra’ is either harmonious and leads to health, or
disorganized in ways that lead to distinct classes of schizophrenia,”
Cloninger said.
The study marks a breakthrough for scientists hoping to treat
patients suffering from the illness. Now that the genetic variations
responsible for the symptoms have been identified, it may be possible to
target specific pathways that lead to schizophrenia.
“In the past, scientists had been looking for associations between
individual genes and schizophrenia,” said Dragan Svrakic, a
co-researcher and professor of psychiatry at Washington University.
“When one study would identify an association, no one else could
replicate it. What was missing was the idea that these genes don’t act
independently. They work in concert to disrupt the brain’s structure and
function, and that results in the illness.”
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