A study that analyzed the DNA of 2,300 people around the world has found dozens of genetic mutations linked to the development of autism, suggesting the causes of autism are more complex than first thought.
The research could also open the door to tests that could help identify children with the condition.
The study, conducted by scientists in Canada, the United States and Europe, analyzed genetic data from 1,000 subjects who had been diagnosed with an autism spectrum disorder and 1,300 who had not. They found that children with autism had dozens of gene mutations in the form of duplicated or missing bits of DNA.
Some mutations were passed down from one parent to a child with autism, while others were not inherited and may have developed during conception. All of the mutations appear to control how brain cells grow and communicate.
The researchers say that the genetic pattern they found suggested the genetic causes of autism are much more complex than they would have thought.
In fact, the findings probably explain only about 3.3 per cent of the genetic origins of autism, and each child with autism appeared to have unique genetic markers associated with his or her condition.
"It is a common disorder but in fact it's a rare genetic variation and each family in a way has their own form of autism," senior study investigator Dr. Stephen Scherer of the Hospital for Sick Children told Â鶹´«Ã½. "And we didn't think about it that way before."
The findings are published in the journal Nature.
The researchers said the findings support the emerging theory that autism is caused in part by numerous genetic variants. However, these genetic changes are found in less than one per cent of the population, and each variant may only account for a small number of autism cases.
But together, they account for a growing number of incidences of the condition, which is known to affect about one in every 165 children.
The research did show that the genetic changes in autistics people appear to cluster along biological pathways, some which had been previously identified. This work uncovered others that until now were not implicated in the development of autism.
According to Scherer, the tests used in the study can be administered now to identify autistic children.
What the study does not answer is how the genetic changes occur.
It's possible that "tiny genetic errors may occur during formation of the parents' eggs and sperm" which then lead to autism from environmental triggers.
And experts say the study will allow scientists to ramp up their research into what causes autism and hopefully lead to the development of treatments for the condition.
"Now that I think we've got a handle on this final common pathway, I think there's going to be very rapid discoveries in understanding at a biochemical level what's gone wrong," said Dr. Peter Szatmari of McMaster University.
Ontario mother Lisa Bond often wondered if something she did caused her son Joshua's autism. Joshua was tested as part of the study, and researchers confirmed he has a genetic abnormality linked to his condition.
Bond told Â鶹´«Ã½ she was happy, "to know that there are answers out there, and hopefully in the future these answers will lead to better treatments and better understanding."
With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip
