Although originally a medical diagnosis first used by Dr. Leo Kanner, today autism is a general term that is often used interchangeably with what health care providers refer to as “pervasive developmental disorders.” Individuals with a pervasive developmental disorder (PDD) have a unique set of symptoms that affect three areas or “domains”: communication, socialization (interaction with others), and behavior. Within this broad category, there are five currently accepted official diagnoses:
- Autistic Disorder
- Asperger Disorder
- Pervasive Developmental Disorder Not Otherwise Specified
- Rett Disorder
- Childhood Disintegrative Disorder
The distinctions between these diagnoses hinge on subtle differences in language development, severity, and age of onset (age at which symptoms first appeared), as well as other features that a health care provider can evaluate. For instance, the diagnosis of autistic disorder requires symptoms in all three of the areas described above, as well as a history of a delay in developing spoken language and onset of symptoms prior to 36 months of age. By contrast, Asperger disorder is an appropriate diagnosis for individuals who show many of the same features of Autistic disorder in all three areas, but who specifically do not have any delay in developing spoken language. Pervasive developmental disorder not otherwise specified (PDD/NOS) is a diagnosis assigned to children who have symptoms in all three areas, but who do not meet the specific diagnostic criteria for any of the other pervasive developmental disorders.
Parents often tell us their child has received several different PDD diagnoses, which may be due to changes in symptoms over time or variability in the methods of assessment. These diagnoses may include the five listed above, or others (not officially recognized medical diagnoses) such as “autism spectrum condition,” “high functioning autism,” or atypical autism.” The only way to diagnose someone with a PDD is through clinical means (such as observation and interviews) — there is no “medical test” that can give a clear diagnosis.