Cluster analysis of autism spectrum disorder symptomatology: Qualitatively distinct subtypes or quantitative degrees of severity of a single disorder?

The decision to collapse several related disorders into a single diagnosis of Autism SpectrumDisorder (ASD) generated significant controversy and debate. There has been mixed evidence asto whether various ASD subtypes are qualitatively distinct or if they exist on a spectrum ofsymptom severity. The present study conducted a two-step cluster analysis of major ASDsymptoms in a sample of 147 young males with ASD aged between 6yr and 18yr with IQ > 70.Results indicated that a two-cluster solution (high and low severity of ASD symptomatology) wasreliable and valid. Further, the construct of challenging behaviour was not a necessary compo-nent of the two-cluster solution, verifying the new conceptualisation of ASD. Further replicationof thesefindings with other subsets of individuals with ASD is needed.