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Researchers Discover DNA Link To Schizophrenia

Posted on: Thursday, 31 July 2008, 08:15 CDT

Two large global studies show that people who lack certain pieces of DNA have a significantly greater risk of getting schizophrenia. The finding could lead to a better understanding of how to diagnose the illness.

The lack of DNA only occurs in less that 1 percent of schizophrenics, but each deletion increases the risk by nearly 15-fold.

Researchers say that studying such irregularities may help them discover new medications by revealing what causes the illness. If enough rare deviations can be found, they might eventually be combined into a test to help diagnose patients, says Kari Stefansson, author of one of the studies, and chief executive officer of deCode Genetics of Reykjavik, Iceland.

Currently schizophrenia must be diagnosed by its symptoms: hallucinations, delusions, and disordered thinking. The disease is more common in men than in women, and is normally diagnosed in early adulthood.

Scientists have previously found deletions and genes that they have linked to schizophrenia risk, but the new development is the first time two independent studies have identified the same two DNA abnormalities. The studies also confirmed a previously known variant that affects 1 in 100 people.

According to Dr. Pamela Sklar of Massachusetts General Hospital, and author of the other paper, DNA deletions are only linked to a small fraction of schizophrenia cases, but it’s not unusual to find a very rare cause of the illness that sheds light on new information that applies abroad.  Discoveries of that nature can lead to treatments for many people.

The studies also found many of the same DNA variants in people with autism, and other psychological disorders.  The findings suggest that the conditions could be interrelated.

Both papers received praise on Wednesday when they were published online by the journal Nature.

"This is tremendous,” said Dr. Linda Brzustowicz of Rutgers University. But because the abnormalities found are only related to a small fraction of schizophrenia cases, it's too early for companies test people for them, she added.

Steffansson’s report included authors from more than a dozen facilities in the U.S., Europe, and China.  They submitted findings from DNA tests in nearly 4,700 people with schizophrenia and more than 40,000 healthy individuals.

Sklar’s report included researchers from 11 centers in the U.S., Europe, and Australia.  They tested nearly 3,400 individuals with schizophrenia and 3,200 healthy people.

Both reports discovered that though the DNA abnormalities were rare in schizophrenia patients, they were far more rare in individuals without the illness.  Researchers say the illness stems from both genetic predisposition and environmental influence, and one researcher warned that the disease is so complex that genes only will only moderately explain the illness.

The two DNA abnormalities found by both studies show a boost in schizophrenia risk 12, and 15-fold.  A third abnormality appears to raise the risk threefold.

Sklar was “absolutely delighted” that both studies found the abnormalities independently.

According to Anne Pulver of Johns Hopkins University, the studies embody a shift in focus for finding genetic abnormalities that may lead to schizophrenia.

Until now, the search has focused on common variants that held little effect on an individual’s risk for schizophrenia.  The new method seeks out the rare abnormalities that play a bigger role.  Researchers hope the new approach will help them detect subgroups of patients with hereditary causes for their illness, leading to better treatments with better outcomes.

In different study led by Professor Michael O’Donovan, from the University of Cardiff Medical School, researchers discovered more common genetic variations held by large groups of people.  The group’s results offer a much smaller role in predicting an individual’s risk of schizophrenia.

"It's very dangerous to say never, but to me, there are so many genes involved, that the idea of predicting whether someone will develop schizophrenia doesn't seem to me very likely," he added

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On the Net:

• deCode Genetics
• Nature
• Information on schizophrenia
• Massachusetts General Hospital

Source: redOrbit Staff & Wire Reports

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