Individuals with mutations in specific genes have a high risk of autism, according to scientists working independently at Harvard, Yale, and the University of Washington in Seattle.

The scientists said they have already identified several genes that lead to an increased likelihood of autism. But there is a possibility that several hundred genes are involved in autism, said Mark J. Daly, an associate professor of medicine the senior writer of the Harvard paper.

“We’re moving away from the single gene Mendelian idea of disorders or the idea that only a few genes cause the effect,” Daly said. “There are many genes in the biological pathways.”

This discovery will allow a better treatment for autism to be developed that targets the mutated genes, according to Daly.

“It’s not good for a predictive model but can help us develop a hard biological model of autism and eventually develop a therapeutic treatment,” Daly said.

The scientists expect to find 25 or more genes by the end of year, said Stephan J. Sanders, a postdoctoral fellow at Yale and lead author of the Yale paper. Although the genes do not allow for diagnosis, it may eventually be possible once they have achieved a comprehensive knowledge of the genes that cause autism, he added. Even more powerful, their findings might lead to a treatment.

“The study of genes helps us understand what autism is at a fundamental level,” Sanders said. “This understanding will help us develop a treatment. Right now we don’t know what autism is, except that it is genetic.”

The scientists at Harvard, Yale, and University of Washington worked independently, only coordinating at the end of their studies when the papers were being submitted for publication, according to Sanders.

The three teams each had papers published Wednesday in the scientific journal Nature.

Sanders and the team at Yale studied 238 families, who each had only one child diagnosed with autism. This process was essential so mutations in specific genes could be found, which would indicate the gene’s link to autism. Sanders said that by the end of the year, the Yale research team plans to have studied 2600 families.

“We see genes as part of a jigsaw puzzle; find enough of them and you can see what the disease is,” Sanders said.

—Staff writer Armaghan N. Behlum can be reached at behlum@college.harvard.edu.