The Construct Validity of Proposed Criteria for DSM-5 Autism Spectrum Disorder

Background: Imminent revisions of diagnostic criteria for ASD beg a number of questions concerning construct validity. For example, should stereotyped language be regarded as a repetitive behaviour (RRB) or as social communication impairment? Is it appropriate that play and imagination deficits be dropped as a symptom of autistic social communication impairment? What is the role being played by sensory sensitivities in the autism phenotype: are they congruent with other aspects of symptom severity?

Objectives: We used 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.

Methods: Participants were 708 verbal children and young people (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 behaviour (RRB) factor, was compared to 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: Our findings suggest that the autism phenotype is inadequately described by DSM-IV-TR criteria, and that the proposed autism dyad of DSM-5 has greater validity. We conclude that the core impairments of ASD are manifestations of separable social communication and RRB dimensions. We have also found support for the hypothesis that sensory abnormalities are best conceptualised as an aspect of RRB. Evidence is emerging that it is ‘time to give up on a single explanation for autism’, and that distinct aetiologies may underpin different dimensions of autistic impairment. We conclude that the time has come to investigate whether the social communication and RRB dimensions we describe are associated with distinct endophenotypes and genotypes.