People with autism may have differences in their genes that are unique to each person, a new international study shows.

The study, published in Wednesday's online issue of the journal Nature, shows the roots of autism may be found in stretches of missing or extra pieces of DNA that can disrupt brain function.

In some cases, researchers can now point to the genetic cause of a child's autism, Stephen Scherer says. (CBC)

"By identifying the genetic causes of autism, we hope in the future to be able to improve the diagnosis and treatment of this condition which can affect children and their families so severely," one of the study's leaders, Tony Monaco of Oxford University's Wellcome Trust Centre for Human Genetics, told a telephone briefing with reporters from London.

The Autism Genome Project of researchers from Canada, the U.S. and Europe studied the genes of 996 people with autism and 1,287 without, all with European ancestry.

"Autism as a clinical condition looks very similar, but the underlying genetics can be different," the team's senior investigator, Stephen Scherer of the Hospital for Sick Children in Toronto, said in an interview.

The study points to genetic clues that will help explain the cause of autism or other medical complications in at least 10 per cent of the families from the Canadian part of the study, Scherer said. Children with autism who are diagnosed early may benefit more from therapy. (Vincent Du/Reuters)

The researchers found people with autism tended to have losses or extra copies of segments of DNA known as copy number variants. The variants can disrupt how genes work.

The variants may be inherited or random. If random, the family has no heightened risk of having another child with autism, data that could influence family planning decisions, Scherer said.

Early diagnosis potential

For now, the findings offer a sort of guide book for clinical geneticists and counsellors to make sense of the genetic changes seen in some individuals with autism, he said.

Gene Rocha of Cambridge, Ont., and his family donated blood samples for genetic testing in the study to try to help improve the quality of life of families in the future. Rocha's eight-year-old son, Logan, has autism. His sister, Olivia, 4, is not affected.

"It's going to be unbelievable for families down the road," Rocha said.

"If you can diagnose a child with autism when they're still an infant, say three months, six months, the family is going to have access to that therapy at the age where it's going to be the most beneficial, and the child is going to get the most out of it. So that's a huge thing."

Knowing which genetic variants can cause autism and understanding the biological pathways may also help in the search for potential drug targets, said the researchers.

Despite the hope triggered by the results, families of people with autism point out they often still face long waits for diagnosis and access to existing treatments.

Other Canadian researchers in the study were from Toronto, Hamilton, Montreal, Halifax, Edmonton, and St. John's.

The study was funded by Autism Speaks (USA), the Hilibrand Foundation (USA), Health Research Board (Ireland), the Medical Research Council (U.K.) and the Genome Canada/Ontario Genomics Institute. Additional support was provided by the U.S. National Institutes of Health and equivalent federal agencies in Canada, France, Italy, United Kingdom, Germany, Portugal and Sweden.