Friday, June 18, 2010

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

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.


Astrid said...

A genetic connection doesn't mean the two disabilities of autism and ID are the same. It just means there is a strong relationship, which is already reflected in the 40% of autistic spectrum people with ID. Similarly |(but mor ein line with feel good stereotypes), there is a genetic link between bipolar disorder and creativity, but one would never say these two are one and the same.

As a side note, it is very saddening that there is so much stigma associated with intellectual disability. I, for one, do not mind being associated with intellectual disability even though I do not personally have it.

Carl said...

one thing with DNA that also needs to be remembered is that DNA can be mutated

this means that there is the distinct possibility that there could be genetic links between the autism and intellectual difficulties simply because a mutation caused by the development of autism (regardless of how) could also have at the same time mutated enough to create the intellectual difficulties.

It should also be noted that even looking at the broad spectrum where 40 to 50% is considered to have intellectual difficulties there is still sufficient numbers involved to draw a direct relation between the two factors (autism and ID)

Lisa Jo Rudy said...

Not sure I buy the idea that autism and intellectual disability are identical disorders... but you're certainly right about the issue of shame related to ID. It's a very, very hard hurdle to leap, too, IMO.

If you could institute an educational program for the general public to overcome the stigma of ID, what kind of program would you put in place? How would you improve the image of people with intellectual disability, and/or educate the general public about how to think about it, treat people, provide for people, etc.?


Ian MacGregor said...

Cancer and death are not the same. There are plenty of people who survive cancer, and of course there are plenty of people who die from other causes. Yet no one would dispute than cancer kills

It's the same way with autism and ID. Autism does not necessarily cause ID but it so often does or mpre properly the genetic problems which lead to autism may often lead to ID

I think they are separate, but closely related disorders.

No one would argue that raising awareness of cancer's deadly aspects helps cancer sufferers by ensuring funds are spent seeking cures.

Hoe odd it is that raising awareness of autism's intellectual disability aspects in the hope it leads to research leading to a cure is by some seen as a bad thing. It is good , no it is great for the person with low-functioning autism. It is only bad for the rosy view perspective of autism.