How is it diagnosed?

Autistic Disorder and Asperger’s Disorder fall under the broader title of Pervasive Developmental Disorders.  Diagnosticians use a variety of assessments, (e.g., the ADOS, the Bayley, the WPPSI, the CARS, the CHAT, the ADI-R and the Vineland) to diagnose these disorders.  The assessments used depend on the chronological age and level of functioning of the patient, and the diagnostician’s preference.

The presence of Autistic Disorder is determined by the assessment across three main areas of functioning: social interactions, communication, and stereotypy (i.e., stereotyped patterns of behavior).  If the patient meets a total of six criteria across at least two of these areas of functioning, then Autistic Disorder is diagnosed (see Diagnostic Statistical Manual for more detail).

Asperger’s Disorder is diagnosed if the patient displays stereotypy and impairment in social interaction, but does not show significant delays in language development.

Pervasive Developmental Disorder (PDD-NOS) is diagnosed when the patient exhibits a severe impairment in social interaction and language development and/or stereotypy is present, but does not meet the criteria for a diagnosis of Autistic Disorder.