Autism researchers welcomed the new paper as valuable progress in understanding some of the causes of a largely inscrutable disorder. "I think this paper is important because it's one in series of ongoing large studies that continue to really chip away very nicely at the mystery of autism," says Dr. Daniel Geschwind, director of the Center for Autism Research and Treatment at the University of California, Los Angeles. (See TIME's photo-essay "A Journey into the World of Autism.")
Since the launch of the international consortium, a collaboration of more than 120 scientists and 50 institutions, at least two dozen or so genes have been identified and associated with autism spectrum disorders (ASDs). Past studies of twins and families have shown that susceptibility to ASDs is primarily genetic, and researchers estimate that 5% to 15% of autism cases can be traced back to specific, known genes. But the complex genetics of the other 85% cases of ASD have been difficult to untangle. Genes may play a role in these children's vulnerability to autism, but many other factors, such as parental age and other unknown environmental influences, may impact whether they actually develop autism's hallmark deficits in social, cognitive and communication skills.
In the new study, researchers have taken a step toward quantifying the influence of certain genetic patterns. After conducting detailed genetic analyses and comparing the genomes of 996 people affected with autism and 1,287 matched controls, they found that those with ASDs were 20% more likely to have so-called copy number variations — abnormalities in the number of copies — of specific genes. These changes affect about 1% of people in the general population. (See how autism numbers are rising.)
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