A cluster analysis exploration of autism spectrum disorder subgroups in children without intellectual disability

Background The heterogeneity in autism spectrum disorder (ASD) remains poorly understood, particularly in individuals without intellectual disability (ID), where phenotypic variability can be most pronounced. The presence of phenotypic subgroups continues to be questioned. This study investigated whether children with ASD without ID are differentiable into clinically meaningful subgroups. Method Data from the ‘gold standard’ ASD diagnostic instruments for 61 children (5–14 years) with ASD without ID were subjected to exploratory cluster analysis. Cognition, language, pragmatic communication, and behaviour were used to explore subgroups. Results Children with ASD without ID could be differentiated into Moderate and Severe Social Impairment subgroups when core ASD symptoms were more closely examined. The Moderate Social Impairment subgroup showed less severe social interaction and communication impairments but greater lifetime severity of restricted/repetitive behaviours. In contrast, the Severe Social Impairment subgroup, with poorer social interaction and communication skills, had lower lifetime severity of restricted/repetitive behaviours. This subgroup also had greater cognitive and language difficulties, and poorer adaptive functioning. Importantly, however, these neurocognitive and functional differences showed only small to moderate associations with the differentiated ASD clinical profiles. Conclusions Evidence of dissociated levels of severity across core ASD dimensions supports the idea that clinically meaningful subgroups within ASD without ID can be identified. The dissociated profiles of ASD features could represent different underlying neurobiological mechanisms for each subgroup. Identifying such subgroups in practice can improve the clinical utility of diagnostic labels in this population. Thus, both categorical and dimensional approaches may be useful in classifying ASD, with neither alone being adequate.