Subtypes of autism by cluster analysis.

Multidisciplinary data from 166 children with autistic spectrum disorders were subjected to cluster analysis. Cross-validation between random halves of the sample showed acceptable consistency of the clustering method. Four clinically meaningful subtypes emerged from the analysis. They did not differ in demographic characteristics but did show, on average, distinct differences in behavioral and cognitive areas. Over half of the sample fell into a subtype described as typically autistic with abnormal verbal and nonverbal communication, aloofness, impaired social skills, and sensory disturbances. Another 19% were similarly autistic but with moderate to severe mental handicap. The remaining children formed two subtypes: a high-functioning Asperger-like group who were overactive and aggressive, and a small group who were impaired in social and language skills, had restricted interests, and a family history of learning problems. This study highlights important differences among children with autism and emphasizes relationships between cognitive functioning and subtypes of the disorder.