11th May 2013 .
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Pervasive developmental disorder not otherwise specified (PDD-NOS) is one of the five autism spectrum disorders (ASD) and also one of the five disorders classified as a pervasive developmental disorder (PDD).
According to the DSM-IV, PDD-NOS is a diagnosis that is used for "severe and pervasive impairment in the development of reciprocal social interaction or verbal and nonverbal communication skills, or when stereotyped behavior, interests, and activities are present, but the criteria are not met for a specific PDD" or for several other disorders.
PDD-NOS is often called atypical autism, because the criteria for autistic disorder are not met, for instance because of late age of onset, atypical symptomatology, or subthreshold symptomatology, or all of these.
It is common for individuals with PDD-NOS to have more intact social skills and a lower level of intellectual deficit than individuals with other PDDs. Characteristics of many individuals with PDD-NOS are:
- Communication difficulties (e.g., using and understanding language)
- Difficulty with social behavior
- Difficulty with changes in routines or environments
- Uneven skill development (strengths in some areas and delays in others)
- Unusual play with toys and other objects
- Repetitive body movements or behavior patterns
- Unusual likes and dislikes
Studies suggest that persons with PDD-NOS belong to one of three very different subgroups:
- A high-functioning group (around 25 percent) whose symptoms largely overlap with that of Asperger syndrome, but who differ in terms of having a lag in language development and mild cognitive impairment. (The criteria for Asperger syndrome excludes a speech delay or a cognitive impairment.)
- A group (around 25 percent) whose symptoms more closely resemble those of autistic disorder, but do not fully meet all its diagnostic signs and symptoms.
- The biggest group (around 50 percent) consists of those who meet all the diagnostic criteria for autistic disorder, but whose stereotypical and repetitive behaviors are noticeably mild.