In the comments, an important question was raised by Harold Doherty, author of the Autism in New Brunswick blog: What will happen to autistic people with intellectual disability in DSM 5?
Although I didn’t mention it in the original post, this was actually something that McPartland et al looked at in their study.
Harold's concern, which he's been raising for some time, is that the wording of the new criteria will actually (and, in his view, deliberately) exclude people with an intellectual disability.
Under the draft version of DSM 5, in order to receive an ASD diagnosis, a person would have to show:
"persistent deficits in social communication and social interaction across contexts, not accounted for by general developmental delays."It's that last part that is the issue for Harold.
The idea, as I interpret it, is to make sure that people getting an ASD diagnosis really are autistic and not merely people who have social difficulties that are a result of developmental delay.
An analogy would be with people who are born deaf or blind; they inevitably have social interaction difficulties but we wouldn't necessarily call them all autistic. In the same way, someone with intellectual disability might struggle in certain social situations because of their poor language and memory skills, but again they wouldn't necessarily be considered to have autism.
Autism is more than just being a little behind in terms of social development. It’s qualitatively different. The challenge is to define those qualities.
This interpretation of the new criteria is entirely consistent with the quotation Harold provides from Cathy Lord, a member of the DSM-5 Neurodevelopmental Work Group:
Catherine Lord… said that the goal was to ensure that autism was not used as a “fallback diagnosis” for children whose primary trait might be, for instance, an intellectual disability or aggression. New York Times, 20 Jan, 2012Clearly, the intent is to stop non-autistic people getting an ASD diagnosis. That isn’t the same thing as saying that, if you’re intellectually disabled, you can’t also be autistic.
So much for the intentions. What about the guidelines in practice?
In one of their analyses, McPartland et al. divided people up according to their IQ. Those with IQs below 70 were considered to have “low cognitive ability”, which I think for our purposes we can treat as being synonymous with intellectual disability.
As in the previous post, I’ve plotted the results with kids achieving a DSM-5 ASD diagnosis in blue (ASD+) and those missing out on a diagnosis in red (ASD-).
As we saw last time, a good chunk of the kids failed to meet DSM-5 criteria for ASD. However, kids with intellectual disability were much more likely to be diagnosed with ASD than were those with IQs above 70. This is the opposite of what we’d expect if DSM-5 really was going to selectively exclude the intellectually disabled.
As I discussed before, we need to treat these findings with a good deal of caution. But I can't see any intention to exclude people with intellectual disability, and there's certainly no evidence at this time that this will happen in practice.