Wikipedia Precis

This revision: 11th May 2013 .
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Pervasive developmental disorder not otherwise specified (PDD-NOS) is one of the five autism spectrum disorders (ASD)[1] and also one of the five disorders classified as a pervasive developmental disorder (PDD).[2]

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.[3]

PDD-NOS is often called atypical autism,[4] 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.[3]

Even though PDD-NOS is considered milder than typical autism, this is not always true. While some characteristics may be milder, others may be more severe.[5]


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.[2] 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[2]

Three subgroups

Studies suggest that persons with PDD-NOS belong to one of three very different subgroups:[8]

  • 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.[8] (The criteria for Asperger syndrome excludes a speech delay or a cognitive impairment.[9])
  • 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.[8]
  • 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.[8]

Useful Links

Cognitive Neuroscience of Autism

Research review by Simon Baron-Cohen


Changes to ASD sub types and diagnostic criteria. US publication, but most countries including UK have referenced DSM-IV historically

Wrong Planet

A community and online resource for people with Asperger's Syndrome. A busy site with forums, blogs, plenty of information and opinion.

Yale Autism Program

The Autism Program at Yale is an interdisciplinary group of clinicians and scholars.


Autism diagnosis in children and young people - clinical guidance

National Autistic Society

The NAS provide training, support, assessment and other services throughout the UK.

ARC Tests and Research Tools

Excellent (non-diagnostic) autism tests from Frith, Baron-Cohen & ilk. Very useful for CPD, research etc


The ARC is the UK's world-leading autism research centre. Several dozens of papers are available for download via the publications section.

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