Study Confirms DSM-5 Autism Spectrum Disorder Excludes Low Functioning, Intellectually Disabled Autistics

The abstract following is for the article  Testing the Construct Validity of Proposed Criteria for DSM-5 Autism Spectrum Disorder, authors William P.L. Mandy, D.Clin.Psy., Tony Charman, Ph.D., David H. Skuse, M.D.Accepted 21 October 2011. published online 05 December 2011. The study participants were 708 children and young persons who had mild to severe autistic difficulties. The authors, as I have highlighted in bold in the abstract, concluded that  the two-factor DSM-5 model for the New Autism Spectrum Disorder (three domains become two, APA, DSM-5, ASD Rationale) was superior to the three-factor DSM-IV-TR model. 

The authors' conclusion that the DSM-5 was a superior autism model was expressly based on the conclusion that "Among higher-functioning individuals, ASD is a dyad, not a triad, with distinct social communication and repetitive behavior dimensions."  No mention in the abstract conclusion is made of whether the same was true for lower-functioning autistic individuals who are not even mentioned in the conclusion.

It appears that, for the authors of this study, there is no need to consider whether the DSM-5 model is superior to the DSM-IV model for lower functioning autistic individuals, including the vast majority of the original classic autistics who suffered from intellectual disabilities.  It seems reasonable to assume that the authors' nonchalance is based on the wording of the DSM-5 which expressly excludes the intellectually disabled from a diagnosis under the DSM-5's New Autism Spectrum Disorder.  If the most low functioning autistics will no longer be included in the DSM-5 New Autism Spectrum Disorder why worry about current  DSM-III and DSM-IV low functioning autistics? 

In other words the authors know which way the wind is blowing in the DSM-5 2013, and beyond, world of autism. The DSM-5's New Autism Spectrum Disorder is for High Functioning Autism and Asperger's only.  Low functioning, intellectually disabled autistics will be found under the Intellectual Developmental Disorders category of the DSM'5's brave new autism world. (ASD - Mandatory Criterion A)

"Objective

To use confirmatory factor analysis to test the construct validity of the proposed DSM-5 symptom model of autism spectrum disorder (ASD), in comparison to alternative models, including that described in DSM-IV-TR.

Method

Participants were 708 verbal children and young persons (mean age, 9.5 years) with mild to severe autistic difficulties. Autistic symptoms were measured using the Developmental, Dimensional and Diagnostic interview (3Di). The fit of the two-factor DSM-5 model, which has a social communication and a restricted, repetitive behavior (RRB) factor, was compared with that of alternative models. In one half of the sample, properties of the DSM-5 model were examined to investigate the validity of specific diagnostic criteria, informing the development of a better fitting DSM-5 model. This was then cross-validated in the remaining “hold-out” half of the sample; and its stability was tested across groups defined by age, sex, and symptom severity.

Results

The DSM-5 model was superior to the three-factor DSM-IV-TR model. It was improved by the removal of items measuring “play and imagination” and “stereotyped and repetitive use of language.” A scale measuring sensory abnormalities was added to the model, and loaded onto its RRB factor. This DSM-5 model fit well in the hold-out sample; was stable across age and sex; and fit adequately in those with clinical and sub-threshold autistic presentations.

Conclusions

Among higher-functioning individuals, ASD is a dyad, not a triad, with distinct social communication and repetitive behavior dimensions. As suggested in the proposed DSM-5 criteria, sensory abnormalities are part of the RRB symptom cluster." [bold emphasis added - HLD]