Scientists on the search for the genetic roots found something surprising. Families with two children diagnosed with autism often did not share the same genetic mutations.

It is giving rise to the theory autism is not inherited, even when it runs in families. The research also proves the genetics of autism is still poorly understood. Theories as to what causes the multiple instances include environmental factors and conditions during the pregnancy.

Children with an older sibling who has autism is seven times more likely to be diagnosed, compared to a child out of the general population. The shared risk is the big question among researchers.

“This is still the million dollar question,” says Stephen Scherer, PhD. Dr. Scherer is the lead author of the study , published in Nature. He’s also the director of the Centre for Applied Genomics at the Hospital for Sick Children.

Researchers looked at biological clues of autism, which is on the rise in the United States. Using 85 families with two children who had been diagnosed, the team sequences the genes of each member.

Genes linked to autism were found in less than half of the participants – or 36 families. Of the 36, only 11 sets of siblings shared the same genetic changes, and only 10 received those changes from their parents.

Siblings that didn’t share the same changes in genes also had different looking autism. One may have issues with language development, while the other could be close to normal.

“I think when physicians who see the kids hear that, they’re not surprised so much because they really see the variability, even between siblings,” Scherer says.

Questions Remain

The study shows that a multitude of questions remain. Researchers are still far away from being able to sequence the gene. Some experts point to possible chemical exposure when the children are young. Others want to see more in-depth research to match up the different behaviors we have associated with autism.

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