Changes On the Horizon: Comparing DSM-5 Autistic Spectrum Disorder with Social Communication Disorder

Background: The arrival of DSM-5 heralds a transition in our understanding of neurodevelopmental disorders; a transition which will have consequences beyond the academic and clinical spheres, reaching into the daily lives of individuals receiving a diagnosis.  DSM-5 proposes a two domain-based definition of Autism Spectrum Disorder (ASD). These domains comprise: i) social communication deficits; ii) restricted, repetitive patterns of behaviour, interests, and activities plus sensory sensitivities. Criteria require symptoms to limit and impair everyday functioning.  Changes from DSM-IV.TR mean those who do not meet criteria in both domains cannot be diagnosed as ‘ASD’. A controversial new construct - Social Communication Disorder (SCD) - will apply to many who would have met PDD-NOS criteria under DSM-IV.TR.

Objectives: The study tests the hypothesis that proposed diagnoses of ASD and SCD can be differentiated on measures of adaptive functioning, pragmatic communication and social communication.

Methods: Criteria for both a diagnosis of ASD and of SCD were operationalized on the basis of data from parent-report (3Di), and ADOS. The 3Di was used to emulate the content of both ASD domains and SCD domains, on the basis of 170 phenotypic items drawn from our computerized database. SCD was defined first by exclusion (not ASD) and second, on basis of scores in the clinical-range on the composite pragmatic language scale of the Children’s Communication Checklist (CCC). Final ASD group; N=43, mean age = 10.6 yrs: SCD group; N=15, mean age = 11.50 yrs. Measures of cognitive ability included WPPSI or WISC. Vineland Adaptive Behaviour Scales (parent-rated) measured adaptive functioning.

Results: Participants were matched for age and IQ. Results demonstrated no significant differences in adaptive functioning existed between the ASD and SCD groups. Both diagnostic groups demonstrated clinically significant levels of impairment relative to population norms. On CCC-based measures of communicative competence (5 subscales, measuring inappropriate initiation, coherence, stereotyped conversation, use of context, and rapport), there were no significant differences between group scores on any subscale. Social communication skills were measured by both parent report (3Di) and by direct observation (ADOS). Parent report found no significant differences between groups, but those with ASD had significantly greater communication impairment as measured by the ADOS.

Conclusions: Young people meeting diagnostic criteria for ASD and SCD have significant impairments in adaptive functioning as well as poor pragmatic communication skills. Direct observation revealed greater impairments in the communication domain of the ADOS in those with ASD (i.e. who met both A and B-scale criteria under DSM-5). Adaptive functioning was similarly impaired in all domains, in both diagnostic groups.