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6. What is Pervasive Developmental Disorder (PDD)–not otherwise specified?

Pervasive developmental disorder–not otherwise specified (PDD–NOS) is a   developmental disability that shares many characteristics with autism.

Often doctors will simply use the shorthand “PDD” when referring to PDD–NOS, but this is incorrect. The term PDD refers to the class of conditions to which autism belongs. PDD is therefore not itself a diagnosis but a group of diagnoses, while PDD–NOS is a diagnosis.

PDD–NOS is probably the most commonly diagnosed condition within the ASD and is sometimes referred to as “atypical personality development,” “atypical PDD,” or “atypical autism.”

Children are diagnosed with PDD–NOS when they exhibit significant difficulties in the areas of social interaction, verbal communication (speech), nonverbal communication (gesture; eye contact), and play, but are too social to be considered fully autistic or any of the other explicitly defined PDDs, such as Rett syndrome or childhood disintegrative disorder. This is why PDD–NOS is sometimes considered a “sub threshold” condition. Put another way, a diagnosis of autistic disorder is made when an individual displays 6 or more of 12 symptoms listed across three major areas: social interaction, communication, and behavior. However, when children display many of these behaviors but do not meet the full criteria for autistic disorder, they may receive a diagnosis of PDD–NOS. Though the symptoms of PDD–NOS are usually manifest by the age of 3 years, studies have demonstrated that these children are usually diagnosed later and receive treatment later than other autistic children. This delay results from the confusion with the diagnosis, the comparatively less-severe behavioral symptoms, and that intellectual deficits are less common. It should be emphasized that this sub threshold category is defined by what symptoms the child lacks from the diagnosis of autism, rather than what symptoms the child has. No specific guidelines for diagnosis are provided.

This lack of clear criteria for this large and diverse group of children presents problems for research on this condition.


Pervasive Developmental Disorder–not otherwise specified (PDD–NOS) - One of the five diagnoses in the autistic spectrum of diseases. The diagnosis of PDD–NOS is used when there is severe impairment in social interaction and verbal and nonverbal communication skills or when stereotyped behavior, interests, and activities are present, but symptoms do not meet the criteria for other autistic disorders.

Developmental Disability (DD) - A disability of a person manifested before the age of 22 and expected to continue indefinitely. Attributable to mental retardation, cerebral palsy, epilepsy, autism, brain injury, or another neurological condition closely related to mental retardation or requiring treatment similar to that required for mental retardation; results in substantial functional limitations in three or more major  areas of life activity.

Diagnosis - Identification of a disease, disorder, or syndrome through a method of consistent analysis.

Atypical autism - A general term for conditions that are close to but don’t quite fit the set of conditions for autism or other specific conditions. This condition is also referred to as pervasive developmental disorder - not otherwise specified or PDD–NOS.



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