PDD-NOS

Diagnostic Overview
Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS) is one of the autism spectrum disorders and is used to describe individuals who do not fully meet the criteria for autistic disorder or Asperger syndrome.

PDD-NOS may be thought of as “subthreshold autism," or a diagnosis one can give a person who has “atypical symptomatology.” 2  In other words, when someone has autistic characteristics but some of their symptoms are mild, or they have symptoms in one area (like social deficits), but none in another key area (like restricted, repetitive behaviors), they may be given the PDD-NOS label.

In the DSM-IV Criteria for a Diagnosis of Pervasive Developmental Disorder Not Otherwise Specified, PDD-NOS  is covered in 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." 1

American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., rev.). Washington DC: Author. (Pg. 84)

When might a person receive a diagnosis of PDD-NOS?
That will vary, of course, but in one study, researchers found that those with PDD-NOS could be placed in one of three very different subgroups: 4

  • A high-functioning group (24%) who resembled people with Asperger syndrome but had transient language delay or mild cognitive impairment (such that they could not receive the Asperger diagnosis which requires no speech or cognitive delay).
  • A group (24%) who resembled people with autism but who had a late age of onset, or otherwise did not meet the criteria for autism.
  • A group (52%) who were autistic-like, but displayed fewer stereotyped and repetitive behaviors.

Intervention and  Treatment Options

Some parents may prefer the label PDD-NOS, feeling it is less stigmatizing than “autism," while others may find agencies and providers have less of an understanding of the label, making it harder to access services.  In any case, an individual diagnosed with PDD-NOS, like individuals diagnosed with autism or Aspergers syndrome, can benefit from earlyintervention, education services and an Individual Education Program (IEP).

In order to determine what treatments and interventions will be most effective for an individual with PDD-NOS, a thorough assessment of all symptoms must be done. The evaluation must examine a wide variety of factors including behavioral history, current symptoms, communication patterns, social competence and neuropsychological functioning.

An individual with PDD-NOS may have completely different strengths and challenges than another individual with the same diagnosis. One treatment that is the most significant and most effective for one child may be completely unnecessary and ineffective for another. As a result, treatments and interventions must be very individualized based on the information gathered from the thorough assessment.

“A treatment method or an educational method that will work for one child may not work for another child. The one common denominator for all of the young children is that early intervention does work, and it seems to improve the prognosis.” – Temple Grandin

Further Research
Research is needed to further investigate whether specific autism spectrum conditions, as yet unnamed, can be teased out of the catch-all category currently called PDD-NOS. There is no question that there are such conditions, that PDD-NOS (or whatever conditions we are bunching in that category for the moment) exists.

  1. On the hypothetical autism spectrum, writes one researcher: “PDD-NOS is a paradoxical clinical entity. Despite its amorphous clinical boundaries and the subtlety of the clinical presentation, PDD-NOS is one of the most important PDDs. Its importance stems from its relationship to autism, its prevalence, and most of all, the impairment that it imparts to those who have it.” 5American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., rev.). Washington DC: Author. (Pg. 84)
  2. Mesibov, G.B. (1997). Ask the Editor: What is PDD-NOS and how is it diagnosed? Journal of Autism and Developmental Disorders, 27(4), 497-498.
  3. Mahoney, W.J., Szatmari, P., MacLean, J.E., Bryson, S.E., Bartolucci, G., Walter, S.D., Jones, M.B., & Zwaigenbaum, L. (1998). Reliability and accuracy of differentiating pervasive developmental disorder subtypes. Journal of the American Academy of Child and Adolescent Psychiatry, 37(3), 278-285.  Abstract
  4. Walker, D.R., Thompson, A., Zwaigenbaum, L, Goldberg, J., Bryson, S.E., Mahoney, W.J., Strawbridge, C.P., & Szatmari, P. (2004). Specifying PDD-NOS: A comparison of PDD-NOS, Asperger syndrome, and autism. Journal of the American Academy of Child and Adolescent Psychiatry, 43(2), 172-80.  Abstract
  5. Towbin, K.E. (2005). Pervasive developmental disorder not otherwise specified. In F. Volkmar et al. (Eds.), Handbook of Autism and Pervasive Developmental Disorders (pp.165-200). Hoboken, NJ: John Wiley & Sons. (pg.166) 
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