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The Validity of Social (Pragmatic) Communication Disorder
The recent revision of the Diagnostic and Statistical Manual (DSM-5) created a new neurodevelopmental diagnosis of Social (Pragmatic) Communication Disorder (SPCD), characterised by severe difficulties with the social use of verbal and non-verbal communication, in the absence of autism spectrum disorder (ASD). The empirical literature on SPCD is exceptionally sparse, and so it is unclear whether SPCD is a distinct, coherent clinical entity. Specifically the following questions pertaining to the validity of SPCD have been raised: (1) are the symptoms of SPCD merely an epiphenomenon of other developmental problems, such as specific language impairment, attention deficit hyperactivity disorder (ADHD), internalising difficulties or conduct problems? (Norbury, 2013); (2) is SPCD really just a new name for elevated autistic traits which would previously have been labelled as pervasive developmental disorder - not otherwise specified (PDD-NOS) (Happe, 2011).
Objectives:
To identify and describe individuals meeting DSM-5 criteria for SPCD, in order to provide information on its validity.
Methods:
We used items from the Children’s Communication Checklist (Bishop, 1998) and the Dimensional, Diagnostic and Developmental Interview (3Di), to create an algorithm which closely mapped onto DSM-5 criteria for SPCD. The algorithm was applied retrospectively within a sample of 1317 young people (mean age = 9.8 years, SD=3.4) who had been assessed at a clinic for high-functioning ASD. Young people with SPCD were compared to those with ASD and to clinic attenders without ASD on measures of language competence, autistic symptomatology and comorbid psychopathology.
Results:
Of the overall sample, 887 (67.4%) met criteria for DSM-5 ASD, and a further 97 (7.4%) met criteria for SPCD. The remaining 333 (25.3%) did not fulfil criteria for ASD or SPCD, and are designated ‘clinical controls’ in subsequent analyses. On both elements of the autism dyad, youths with SPCD scored intermediate between ASD and the clinical controls. Of the people with SPCD, a quarter (n=27, 27.8%) met DSM-IV criteria for PDD-NOS, with most others (n=59, 60.8%) not fulfilling DSM-IV criteria for any autistic diagnosis. Despite their greater difficulties with the social use of language, the SPCD participants did not score any worse than clinical controls on Children’s Communication Checklist scales measuring ‘syntax’ and ‘intelligibility and fluency’, which are non-pragmatic aspects of language. Also, on the Strengths and Difficulties Questionnaire (Goodman, 1997), they did not show higher levels of social, conduct or internalising problems than controls, although they did have moderately higher levels of ADHD symptomatology (Cohen’s d=.43, p<.05). SPCD children had fewer peer problems (d=.52, p<.05) and were more prosocial (d=.52, p<.01) than those with ASD.
Conclusions:
On balance, our findings are supportive of the validity of SPCD. They do not support the claim that SPCD is a marker for specific language impairment, or that it is just an epiphenomenon of behavioural and emotional problems: compared to clinical controls, youths with SPCD had circumscribed social communication difficulties, without elevated levels of structural language problems or internalising and externalising psychopathology. Furthermore our findings do not support the notion that SPCD is merely the DSM-5 synonym for DSM-IV’s PDD-NOS.