Article # 341. What is PDD-NOS?

What is PDD-NOS?

PDD-NOS stands for Pervasive Developmental Disorder-Not Otherwise Specified. Psychologists and psychiatrists sometimes use the term “pervasive developmental disorders” and “autism spectrum disorders” (ASD) interchangeably. As such, PDD-NOS became the diagnosis applied to children or adults who are on the autism spectrum but do not fully meet the criteria for another ASD such as autistic disorder (sometimes called “classic” autism) or Asperger Syndrome.

Like all forms of autism, PDD-NOS can occur in conjunction with a wide spectrum of intellectual ability. Its defining features are significant challenges in social and language development.

Some developmental health professionals refer to PDD-NOS as “subthreshold autism." In other words, it’s the diagnosis they use for someone who has some but not all characteristics of autism or who has relatively mild symptoms. For instance, a person may have significant autism symptoms in one core area such as social deficits, but mild or no symptoms in another core area such as restricted, repetitive behaviors.

As a diagnosis, PDD-NOS remains relatively new, dating back only 15 years or so. As a result, some physicians and educators may not be familiar with the term or may use it incorrectly.

The current Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) spells out the criteria for a diagnosis of PDD-NOS. Unfortunately, this description consists of a single paragraph, which mainly asserts what it is not:

"This category should be used when there is severe and pervasive impairment in the development of reciprocal social interaction associated with impairment in either verbal or nonverbal communication skills or with the presence of stereotyped behavior, interests, and activities, but the criteria are not met for a specific Pervasive Developmental Disorder, Schizophrenia, Schizotypal Personality Disorder, or Avoidant Personality Disorder. For example, this category includes “atypical autism” – presentations that do not meet the criteria for Autistic Disorder because of late age at onset, atypical symptomatology, or subthreshold symptomatology, or all of these."

More helpful, perhaps, are studies suggesting that persons with PDD-NOS can be placed in 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. (Asperger syndrome does not generally involve speech delay or cognitive impairment).
• A second group (around 25 percent) whose symptoms more closely resemble those of autistic disorder, but do not fully meet all its diagnostic signs and symptoms.
• A third group (around 50 percent) who meet all the diagnostic criteria for autistic disorder, but whose stereotypical and repetitive behaviors are noticeably mild.

As these findings suggest, individuals with PDD-NOS vary widely in their strengths and challenges.