Cognitive Profiles, Phenotypic Heterogeneity and the Severity of Symptoms in Autism Spectrum Disorder

Background: Autism spectrum disorder (ASD) is characterised by a high degree of phenotypic heterogeneity. This heterogeneity is primarily the result of individual differences in cognitive profiles and the severity of autistic symptoms. Previous research has suggested that cognitive abilities may ameliorate the severity of autistic symptoms in certain cases. Objectives: Thereby, implying that the autism spectrum could be composed of distinct subgroups with differing cognitive profiles that index different severity phenotypes as opposed to a severity gradient of autistic symptoms that exists independently of cognitive abilities. Methods: The verbal IQ, performance IQ and severity metric scores (severity of symptoms) of 534 participants were explored using hierarchical cluster analyses (namely single linkage, average linkage & complete linkage). Results: After subjecting the data to a series of hierarchical clustering analyses and validation techniques, a 5-cluster solution produced by the complete linkage hierarchical clustering algorithm, was chosen as the best fit for the data. Conclusions: The results of this study are discussed in terms of previous research and their possible implications for defining ASD heterogeneity, genetics and the efficacy of autism specific interventions.