Tuesday, July 26, 2011

Clinic Notes: The Genetics of Autism

Most of us who have been treating autism for a long time have accepted that autism is a genetic disorder. When parents, who have a child with autism, inquire about having another child, we often recite the concordance rates for them. In other words, what are the odds of having another child with autism? But I have always wondered if autism is a genetic disorder, why the sudden rise that is now epidemic. What changed all of a sudden genetically to cause the epidemic? It is unlikely that people with the autism gene(s) started mating together all at once. Something more than genetics have to be involved to account for the dramatic in autism.
In a recent study, the genetics of autism has been turned upside down. Twins were identified in the California Department of Developmental Services database who had an autism diagnosis. Of these 192 pairs of twins, which had at least one twin diagnosed with autism, the study found a concordance rate of 77% for identical twins and 31 % for fraternal. These figures are in similar to previous studies. But when these results were analyzed by a computer model that looked at the role of genetic and environmental factors the story changed. Now genes accounted for 38% of the risk factors and environmental 58%. Of course the study has been criticized.

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