By Mary Elizabeth Dallas
TUESDAY, July 22, 2014 (HealthDay News) -- One of the largest studies ever conducted into the genetic origins of a psychiatric disorder has uncovered 83 new sites on chromosomes that harbor inherited genes tied to schizophrenia.
The findings, made by an international team of researchers, now bring the total number of common gene variants linked to the disorder to 108.
Although these schizophrenia-associated genes aren't specific enough to be used as a test to predict who will or will not develop the illness, researchers say they might someday be used as a screening tool for high-risk people who may benefit from preventative treatments.
Right now, the total group of schizophrenia-linked genes "only explains only about 3.5 percent of the risk for schizophrenia," Dr. Thomas Insel, director of the U.S. National Institute of Mental Health, said in an agency news release. However, "even based on these early predictors, people who score in the top 10 percent of risk may be up to 20-fold more prone to developing schizophrenia."
Prior research had only identified about 30 common gene variants linked to schizophrenia. In looking for more clues to the molecular basis of the disorder, an international team of more than 500 scientists at more than 80 research institutions in 25 countries re-examined all available schizophrenia gene samples from people with schizophrenia.
The combined data involved more than 37,000 people with schizophrenia and 113,000 people without the disorder.
The analysis looked at people's complete genomes -- the "map" of DNA that makes up a human. Out of a pool of roughly 9.5 million gene variants, the study authors found 108 sites on various chromosomes that appear to be linked to schizophrenia.
The newly discovered sites are grouped around pathways tied to certain processes associated with the disorder. These include communication between brain cells, as well as pathways involving learning, memory and immune function. One site was even focused on a specific target for schizophrenia medication, the study revealed.
One association was confirmed with a variation in a gene that codes for a receptor for dopamine -- a brain chemical messenger that is a known target for drugs used to treat schizophrenia.
The researchers believe that even more genetic clues to schizophrenia could be uncovered in studies with even larger numbers of patients.
"These results underscore that genetic programming affects the brain in tiny, incremental ways that can increase the risk for developing schizophrenia," Thomas Lehner, chief of NIMH's Genomics Research Branch, said in the news release. "They also validate the strategy of examining both common and rare [gene] variation to understand this complex disorder."
The study was published online July 22 in Nature.