CDC Autism Expert: 40% of Persons with an Autism Spectrum Disorder Also Have an Intellectual Disability
Posted Jun 04 2010 3:49am
I have commented on several occasions about the fact that many persons with Autistic Disorder also have Intellectual Disabilities. That fact is a reference to Autistic Disorder as it currently exists in the DSM-IV and excludes, by definition, the many persons with Aspergers Disorder one of the Pervasive Developmental Disorders now commonly referred to as Autism Spectrum Disorders. I have pointed out that the Canadian Psychological Association has referenced studies indicating that 80% of persons with autism ... excluding Aspergers .... have an intellectual disability or cognitive deficit. I have pointed out that two surveys conducted by the CDC (2004 and 2006) indicated that 41-44% of persons with Autism Spectrum Disorders, also have intellectual disabilities. Since the Autism Spectrum includes all those with Aspergers who, by diagnostic definition are not intellectually disabled, the CPA and CDC approximate figures are consistent: approximately 80% of those with Autistic Disorder are intellectually disabled and approximately 40% of those on the entire "spectrum" of ASD's are intellectually disabled.
The reactions by SOME persons with High Functioning Autism and Aspergers and SOME parents of children with High Functioning Autism and Aspergers to this information have not always been polite. Some have claimed that somehow my use of these reported facts is wrong although I have never seen a coherent explanation for that claim. In a recent interviewin the CMAJ Dr. Marshalyn Yeargin-Allsopp , a medical epidemiologist at the CDC, confirms the information set out above. Dr. Yeargin-Allsopp commented on the expansion of the autism definition changes that have taken place since the 1980's:
"But the autism umbrella has since widened to include milder forms, says Dr. Marshalyn Yeargin-Allsopp, a medical epidemiologist at the CDC. For example, it now includes Asperger syndrome, where the sufferer is socially impaired, but experiences typical language development.
Another difference between past and present autism diagnosis involves the presence of intellectual disabilities, adds Yeargin-Allsopp. During the 1960s and 1970s, the vast majority of those diagnosed with autism had an intellectual disability but today, only about 40% have one."
Autistic Disorder is the current diagnostic category (although that will be changed in the DSM-5) which would include those who would have been diagnosed with autism in the 1960's and 1970's. That is the category where the vast majority as Dr. Yeargin-Allsopp states also have intellectual disability. It is only the inclusion in the broad definition of "autism" of Aspergers Disorders, which by definition includes no one with intellectual disability, that lowers the percentage of persons with autism who also have an intellectual disability from the 80% figure to the 40% figure. Those with Autistic Disorder are still in the 80% range of "co-morbidity".
It is crystal clear that these authorities assert that 80% of persons with Autistic Disorder are also intellectually disabled. By pretending that these conditions are "co-morbid", unrelated, coincidental conditions we are ignoring the obvious relationship between them. We are ignoring the fact that classic autistic disorder is a form of intellectual disability.
The fact that 80%, even an unspecified "vast-majority", of those with Autistic Disorder also have an intellectual disability is not a coincidence. It is time now to acknowledge that fact before the DSM-5 arrives to further expand the definition of autistic disorder and further obscure the harsher realities of autistic disorder as we know it today.