A review of subtyping in autism and proposed dimensional classification model.

Autism has been divided into subtypes based on social interaction/communication, developmental level, or both. The validity of subtyping systems and the 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 presence 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 longitudinal data collection are included.