This study took another look at the IQ issue and found that intellectual disability (IQ <70) occurred in 55% in ASD including under 20% with moderate to severe ID (IQ <50)— as opposed to the older work that found ~ 75%. 25% had average IQ, < 3% had above average.
I’m not sure how useful or relevant this is, considering the tendency for wide discrepancies between the verbal and non-verbal components which can result in no “meaningful” IQ (to indicate expected functioning) being calculable. I know of someone with a 50 point difference- above average in verbal, borderline intellectual disability in performance. An outlier maybe, or a misdiagnosis (had meningitis when young)?
The study did look at adaptive behaviour which is perhaps a better indication of how ASD shows up when ‘getting by in the world as it is’.
“ Overall adaptive outcome was significantly lower than IQ and the discrepancy was most notable in the high IQ subgroup, where adaptive behaviour scores lagged by 35 points behind IQ.”