Clinical evidence that Asperger's disorder is a mild form of autism.

Objective: The aim of this study is to obtain clinical evidence to test the hypothesis that Asperger's disorder (AD) is a mild form of autism (AU).

Method: A 78-item Likert scale (the RAADS) was administered to 25 adults with AD and 19 with AU (ages, 18-65 years) to assess presence, type, and duration of symptoms.

Results: The following results were found: (a) subjects with AD and AU have similar symptoms throughout adulthood (responses to 72 of 78 questions were not significantly different); (b) subjects with AD had a significantly fewer total number of symptoms; (c) subjects with AD reported nonsignificantly fewer symptoms in the DSM-IV-TR domains of social interaction and repetitive patterns of behavior; and (d) subjects with AD had significantly fewer symptoms in the communication domain.

Conclusions: The data support the hypothesis that AD is a mild form of AU, and that they share a common etiology and developmental neuropathology. It appears warranted in future diagnostic manuals to incorporate AU and AD into 1 diagnostic category such as, "Autism Spectrum Disorder, (with modifiers, severe, moderate, mild, atypical, and Asperger's type)."