I have noticed many adults diagnosed with Asperger's Syndrome (also know as high-functioning autism) speak FOR persons with autistic disorder and moderate to severe Intellectual Disability (two separate diagnoses).
Intellectual Disability (ID) is a developmental disability that is known to present with Down Syndrome, a neurological, chromosomal condition. Some persons with ASD can also have diagnoses of Intellectual Disability or cognitive challenges - ranging from very mild to extremely profound.
Not all persons with autistic disorder have Intellectual Disability. Some persons with high-functioning autistic disorder have mild or very mild cognitive challenges (diagnosis or not).
Life for people with Autism Spectrum Disorders (ASD's) can be highly stressful, worrisome, anxiety-ridden, challenging, extremely difficult, traumatic, chaotic, and many times, just plain UGLY. Many of these things are caused by ASD ITSELF, NOT society.
For people with both a diagnosis of ASD AND Intellectual Disability, communication - both verbal and non-verbal, academics, self-care skills, adaptive behavior and social skills can develop much more slower or not at all. People with ASD, Intellectual Disability, or cognitive challenges have difficulty with the aforementioned life skills with respect to chronological age.