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Autism and Intellectual Disability, Two Disorders or One? The Genetic Link

Posted Jun 18 2010 3:23am
The recent release of results from the major autism genome study made headlines around the world some of which inaccurately portrayed the study as demonstrating that autism is entirely genetic with no environmental triggers and, heaven forbid, no possible vaccine connections. While any knowledge is theoretically helpful the almost exclusive focus over the last two decades  on genetic autism research to the near exclusion of environmental autism research has probably slowed, if not prevented, our coming to fully understand what causes autism and what may help in curing autism.  The recent study does, according to some reviews, offer some hope of treatment down the road. There may also be some help for those persons with autism disorders and intellectual disability who suffer from being autistic and intellectually disabled and from the stigmatization that results, especially within the so called "autism community",  from being intellectual disabled. 

It is difficult to glorify autism as a different way of thinking, one which has allegedly blessed humanity with gifts  from Mozart to Einstein, while acknowledging that approximately 80% of persons with Autistic Disorder and at least 40% of all persons with Autism Spectrum Disorders also have intellectual disabilities.  While the mainstream media tends to ignore the realities of autism and intellectual disabilities in favor of the feel good "aren't they smart" stories there is outright shame and hostility felt by some in the so called autism community who do not want to be associated with, or have their "autism spectrum" children associated with intellectual disability. 

The shame and hostility felt by  some in the "autism community",  towards  intellectual disability  is blatant but  not discussed except from the perspective of high functioning persons with autism and Aspergers.  Interestingly enough the recent autism genome study may provide information which may help combat the prejudice against acknowledging the autism and intellectual disability connection.

Stephen Scherer one of the study authors, and director of the McLaughlin Center and the Center for Applied Genomics at The Hospital for Sick Children and the University of Toronto, and Andy Shih  vice president of scientific affairs at Autism Speaks, which helped fund the study. Shih served as key facilitator of the Autism Genome Project Consortium were interviewed about the Autism Genome Project study report for an article in  Bloomberg Businessweek . They made some interesting comments about autism and intellectual disability genetic connections


"The researchers compared the genomes of nearly 1,000 people with autism spectrum disorder (ASD) and about 1,300 healthy controls.
On average, participants with ASD had 19 percent more CNVs than the controls. Most of the CNVs were inherited from parents while others appeared for the first time in the autistic individual.
"About 6 percent of these occur as new CNVs in autistic individuals but the vast majority are rare, inherited CNVs," Scherer explained.
"With autism, there's a higher likelihood of having CNV's in their genes, especially genes realted to intellectual disability," Shih stated. 
About 40 percent to 50 percent of kids with autism also have intellectual disabilities, Scherer pointed out.
There were also commonalities with other disorders, including schizophrenia, Shih said."

Scherer's reference to 40-50 percent of kids with autism having intellectual disabilities is a reference to kids on the autism spectrum of disorders.  Since none of the kids diagnosed with Aspergers would have intellectual disabilities by definition, and since PDD-NOS cases tend to be milder, that estimate is consistent with the 80% of persons with autism (excluding Aspergers) having intellectual disability figure approximated by the Canadian Psychological Association and is consistent with the vast majority label used by Dr. Yeargin-Allsop, autism expert with the CDC. Without  KWibbling over these approximate numbers and without going once more into any imaginary breaches this information clearly shows a genetic connection between autism and intellectual disability. 

To this humble father of a son with Autistic Disorder , who is not ashamed of his son's Intellectual Disability,  it appears that a common genetic basis implies that the conditions may in fact just  be part of one neurological disorder and are not in fact separate conditions at all.
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