A couple of weeks ago, I posted on a paper by Mandy and colleagues, which aimed to better characterise kids meeting current (DSM IV-TR) criteria for PDD-NOS (Pervasive Developmental Disorder Not Otherwise Specified). Their conclusion was that most of these kids had social and communication difficulties but not the repetitive and stereotyped behaviours (RSBs) that would have given them a full 'autistic disorder' diagnosis.Under proposed revisions to diagnostic criteria (DSM 5), PDD-NOS is supposed to be subsumed by a broader category of "Autism Spectrum Disorder". However, Mandy et al. pointed out that the proposed criteria for Autism Spectrum Disorder require evidence of RSBs, and so would actually exclude most of their PDD-NOS kids.
In a new paper, Prof Francesca Happe, a member of the DSM-5 working group, outlines the rationale for the proposed DSM 5 changes affecting autism spectrum disorders. The paper overlaps to a large extent with her excellent blogpost on the SFARI website. However, she also references the Mandy et al. paper, acknowledging that many individuals with PDD-NOS may miss out on an Autism Spectrum Disorder diagnosis because they don't have repetitive or stereotyped behaviours.
Here's what she has to say:
“Recently, Mandy et al. raised concerns that many children currently receiving [a PDD-NOS] diagnosis will not meet proposed DSM-5 criteria for ASD because of a lack of restricted / repetitive behaviour. For these children, the proposed new neurodevelopmental diagnostic category of social communication disorder will be relevant. This diagnosis, it is hoped, will more clearly and accurately capture the pattern of impaired social and communication abilities seen in the largest subgroup now labeled PDD-NOS”.
On the DSM 5 website, the new disorder is defined more formally:
"Social Communication Disorder (SCD) is an impairment of pragmatics and is diagnosed based on difficulty in the social uses of verbal and nonverbal communication in naturalistic contexts, which affects the development of social relationships and discourse comprehension and cannot be explained by low abilities in the domains of word structure and grammar or general cognitive ability."
Effectively, SCD seems to be official recognition for what researchers and practitioners have previously referred to as "Pragmatic Language Impairment" rather than a replacement for PDD-NOS. The emphasis is very much on the communication side of things, particularly conversation skills, with a suggestion that social difficulties are a secondary consequence of impaired communication. That's my interpretation at least.
As Happé suggests, it seems likely that many people who currently reside in the PDD-NOS pigeon hole would meet the SCD criteria. However, I'm not sure that the criteria necessarily capture the extent of the issues they face. As Will Mandy mentioned in his comment to my post:
"Our clinical experience is that children with PDD-NOS (i.e. mainly individuals with severe autistic social-communication difficulties, but without high levels of repetitive and stereotyped behaviours) are similar to those with a full autism diagnosis in terms of their functional impairment."
How this will all play out in practice in terms of access to services and interventions, I don't pretend to know. I'd certainly welcome comments from people better informed than I.
Reference
Happé F (2011). Criteria, Categories, and Continua: Autism and Related Disorders in DSM-5. Journal of the American Academy of Child and Adolescent Psychiatry, 50 (6), 540-2 PMID: 21621137
Related posts
What is PDD-NOS?
Further reading
Dorothy Bishop: Pragmatic language impairment: A correlate of SLI, a distinct subgroup, or part of the autistic continuum? [PDF]