Spectrum or subtypes? A latent profile analysis of restricted and repetitive behaviours in autism

Background: Autism Spectrum Disorder (ASD) is a heterogeneous condition. One way of understanding this heterogeneity is by investigating whether homogenous subgroups within the autism population exist. Some studies have attempted to do this by looking at social and communication skills. However, few studies have looked at subtyping using restricted and repetitive behaviours. While restricted and repetitive behaviours form part of the core features of autism, their presentation is diverse across different individuals on the spectrum. The aim of this study was to determine if restricted and repetitive behaviours could be used to identify potential subtypes of autism. Method: This study used unsupervised clustering algorithms to differentiate subgroups of individuals on the autism spectrum based on their scores on the Repetitive Behaviour Scale-Revised (RBS-R). Results: Three groups were found that reported low, medium and high levels of restricted and repetitive behaviours. These groups also differed on a range of clinical measures including problematic behaviours, autistic traits and adaptive behaviours. Conclusions: Our findings indicate that subgroups of individuals with autism can be identified based on their level of restricted and repetitive behaviours. This highlights that restricted and repetitive behaviours may be best understood under a dimensional continuum of severity. This has implications for our understanding of the non-social characteristics of autism.