Scientists have linked more than 100 spots in human DNA to the risk of developing schizophrenia, casting light on the mystery of what makes the disease tick.

Such work could eventually point to new treatments, although these are many years away. Already, the new results provide the first hard genetic evidence to bolster a theory connecting the immune system to the disease.

Researchers from around the world collaborated in the biggest genomic mapping of schizophrenia, for which scientists had previously uncovered two dozen risk-related genes.

The study included the genetic codes of more than 150,000 people - nearly 37,000 of them diagnosed with the disease. Researchers found 108 genetic markers indicating a risk of getting the disease, 83 of them not previously reported. They say there are likely more yet to be found.

"It's a genetic revelation. Schizophrenia has been a mystery," said study co-author Steve McCarroll, director of genetics for the Broad Institute of MIT and Harvard. "Results like this give you things to work on. It takes it out of the zone of guesses about which genes are relevant."

The results were released on Monday by the journal Nature.

It takes large studies to ferret out genes tied to schizophrenia risk because each gene generally has only a very weak effect.

Schizophrenia is a debilitating mental disorder that makes it hard to tell the difference between what is real and not real. It affects about one out of every 100 people. Studies estimate that the disorder costs $60 billion in the US each year. Scientists have long known that genes play a part, and this work further confirms that.

The results are a "big step" toward finding drug therapies, said study lead author Dr Michael O'Donovan, deputy director of the MRC Centre for Neuropsychiatric Genetics and Genomics at the Cardiff University School of Medicine in Wales. While 108 genetic markers are a lot, the study authors say they tend to implicate a narrower group of biological functions, giving some but not too many hints for scientists to pursue.

"It's a map or maze. It's telling you were to start, not where to end," O'Donovan said.

Scientists who didn't work on the study were excited by the possibilities it opens up.

"This makes me more optimistic than I was yesterday," said American Psychiatric Association President Dr Thomas Summergrad, psychiatrist-in-chief at Tufts Medical Center.

Dr Thomas Insel, director of the National Institute of Mental Health, which funded the work, said the study provides useful hints about the biology of the disease, especially the link to the immune system.

"This really is a big step forward," Insel said. "It's not an answer; it's a step forward toward an answer."

Scientists already knew that families with autoimmune disorders tend to have higher rates of schizophrenia, and there's been a link between certain viral infections in the second trimester of pregnancy and higher rates of schizophrenia in offspring, Insel said.

With the new work, "now it's very clear that there's something going on in the immune system" with schizophrenia, said Eric Lander, founding director of the Broad Institute, which was heavily involved in the research.

(China Daily 07/23/2014 page10)