If you define MR by nothing but IQ score and lack of age-level adaptive skills, then many autistics are mentally ret*d, probably something like 25-30%. But that's the trouble; MR isn't one big blob of sameness even when autism isn't involved. The IQ/adaptive-skill definition is the official one, but it also doesn't take into account the differences in cognition. Plus, IQ doesn't seem to really say much about an autistic person because the subscores are scattered all over the place most of the time. Not that IQ testing is completely useless, because it can pinpoint what you're good/bad at doing, but that number says a lot less about an autistic person than it would about somebody whose skills were similar from area to area.
There is a higher rate of autism as comorbid with other disorders that cause mental retardation: Fragile X, Down syndrome, and I think fetal alcohol syndrome. Rett syndrome almost always results in MR, and by definition always results in autism. Seizures are associated with both things... The two diagnoses do have some things in common, though where the connections are still seems to be anybody's guess.
18 Sep 2008, 12:41 pm
