A review of subtyping in autism and proposed dimensional classification model

Autism has been divided into subtypes based on social interaction/communica tion, developmental level, or both. The validity of subtyping systems and t he extent to which they overlap were examined. According to this review, a single subtyping system capable of accounting for the symptom heterogeneity in autism has not yet been proposed; however, evidence supports the presen ce of a three-factor continuum containing at least four subgroups. Foremost among directions for future research is the need for comprehensive studies in which medical screening, careful selection of measures, and longitudina l data collection are included.