An international team of scientists including several Canadians has discovered genetic links that put children at greater risk of developing autism. About 1,500 families offered DNA to scientists searching for a cause for autism spectrum disorder. The results appear in Sunday's issue of Nature Genetics.
Stephen Scherer of the Hospital for Sick Children in Toronto led the Canadian arm of the research, identifying two key genetic causes for autism.
"Now we can think about this condition in a much different way," said Scherer. "We have an understanding of what's going on in the developing brain in these individuals so we can think about ways to actually deal with this issue."
The work involved abnormalities in chromosomes, gene codes and proteins. Between seven to 12 per cent of the families showed individuals sharing possibly detrimental chromosome abnormalities.
A linkage analysis that searched for regions of the genome that might be shared by individuals with autism spectrum disorder turned up a region on chromosome 11 that has not previously been linked to risk of developing autism.
Autism affects one in 160 children. The complexity of the genetics helps explain why it is described as a spectrum, with no two children exactly alike. Environmental factors may also play a role, scientists say.
The Fenton family of Halifax is a case in point. Liam, 14, has Asperger's syndrome. He is able to do Grade 8 schoolwork but has problems relating to others. His 10-year-old brother, Rhys, has a more classic form of autism and has difficulties with language, learning and social interactions.
"We need to find out why," said their mother, Jo-Lynn Fenton. "Obviously, I have two children with autism, somebody has no children with autism, so there's a reason, and the best way to find out is to look at what's different."
The findings may help steer scientists toward new drugs and behavioural therapies tailored to specific children or groups of children, said Dr. Lonnie Zwaigenbaum, director of the Autism Research Centre in Edmonton.
"At some point it may be that this kind of genetic research identifies subgroups of children with autism where the response to intervention may actually somehow relate to the genetics."
New treatments are years away, but the findings may help parents come to terms with why their children are different, and help them to understand that the disorder is not due to something they did during pregnancy.
The study also underlines that if one child is born with autism, there is a greater likelihood their siblings will be, as well.