A recent study examined adult outcomes on education, vocation, independence, friendships and intimate relaitonships, for people with autism spectrum disorders. Comparisons were made between adults diagnosed with ASD in childhood and those diagnosed in adulthood, and between people with and without comorbid intellectual disability. It was found, not surprisingly to me, that the presence of intellectual disability was a significant predictor for poor functioning. This is, however, not supportive of different forms of autism, but rather, of the fact that multiple disabilities interact and complicate a person’s situation, usually leading to poorer outcomes as compared to people with either disability alone. I’d have liked to have seen an analysis of the outcomes of people with and without comorbid mental illness, too, but I assume there is a reason this wasn’t done.
With regard to comparisons between people diagnosed in childhood to those diagnosed in adulthood, there was no difference in functioning when people were assessed prior to age 25. In other words, for autistics under age 25, there is no reason to assume they must function better or worse if they’re diagnosed after age 18, than those diagnosed in youth. For those who were over 25 at the time of assessment, there was a difference in functioning between those diagnosed in childhood and those diagnosed in adulthood, but this difference may be explained by the fact that those diagnosed in adulthood were on average about ten years older than the childhood-diagnosed group at the time of assessment. Therefore, they had approximately an extra decade to “catch up” in functioning. It is quite possible that the childhood-diagnosed group would function at an equivalent level if they’d been of the same age to the group diagnosed in adulthood.
The authors, lastly, emphasize the extreme variability in functioning found particularly within the group without intellectual disability. Note, however, that this was the vast majority, so I don’t think there is any reason to conclude yet that those with intellectual disabilities are uniform in functioning; their subgroup size may’ve been too small to be able to judge that. The attainment of intimate relationships was the goal least likely to be achieved, but even on this domain, there were people who achieved appropriate functioning. With regard to the other domains, there was huge variability, from people living in isolation on disability benefits to a successful university professor. It is unclear what factors actually influence these outcome variables: the authors say that few people studied had ever received targeted interventions (ABA, etc.), but a generally supportive school and home environments did contribute to better adult outcomes.
Marriage S, Wolverton A, and Marriage K (2009), Autism Spectrum Disorder Grown Up: A Chart Review of Adult Functioning. J Can Acad Child Adolesc Psychiatry, 18(4):322-328.