Conceptualizing skills that are most critical in diagnosing autism

•Debate exists over the nature of autism spectrum disorders (ASD).•Identifying symptoms that best differentiates ASD from other developmental disorders is warranted.•Major changes in the DSM criteria for ASD break up continuity in defining and treating the disorder.

Autism spectrum disorders (ASD) consist of a broad but heterogeneous group of symptoms. This factor has resulted in a debate as to whether the disorder is a unitary construct or a group of related disorders with a similar symptom presentation. Additionally, some core symptoms are seen in other developmental disabilities such as intellectual disability. This review covers these and related issues in the context of what symptoms are most critical for diagnosing ASD and distinguishing it from other developmental disabilities.