# Pervasive developmental disorder not otherwise specified
**Pervasive developmental disorder not otherwise specified** (PDD-NOS) was a diagnostic category in the DSM-IV classification of the [American Psychiatric Association](https://www.edgepedia.org/american-psychiatric-association), used for individuals with severe impairments in social interaction and communication suggestive of autism who did not meet the full criteria for a specific pervasive developmental disorder such as autistic disorder or Asperger's disorder.[1](https://www.hogrefe.com/ch/shop/media/downloads/sample-reports/9780889373938_lese.pdf) • [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10217468/) It was introduced in DSM-III-R (1987) and eliminated in DSM-5 (2013), which folded it, together with autistic disorder and Asperger's disorder, into the single category of autism spectrum disorder.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10217468/) • [3](https://pmc.ncbi.nlm.nih.gov/articles/PMC4929984/) • [17](https://pubmed.ncbi.nlm.nih.gov/1483975/)
| Key fact | Detail |
|---|---|
| Status | DSM-IV pervasive developmental disorder subtype; deleted as an entity in DSM-5 (2013) and subsumed under autism spectrum disorder[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10217468/) • [4](https://pubmed.ncbi.nlm.nih.gov/23456348/) |
| Definition | For individuals with problems suggestive of autism who did not meet full criteria for that condition; DSM-IV-TR contained no specific diagnostic criteria for PDD-NOS[1](https://www.hogrefe.com/ch/shop/media/downloads/sample-reports/9780889373938_lese.pdf) • [5](https://www.sciencedirect.com/science/article/abs/pii/S1750946706000080) |
| Clinical profile | In a 2004 comparison, PDD-NOS children scored between autism and Asperger syndrome on functioning measures but had fewer autistic symptoms, especially repetitive stereotyped behaviors, than both (chi2 = 11.06, p = .004)[6](https://pubmed.ncbi.nlm.nih.gov/14726723/) |
| Reliability | Agreement among three experienced blind raters on whether a child had PDD-NOS versus autism was poor[7](https://mentalhealth.bmj.com/content/1/4/121) |
| DSM-5 transition | Individuals with a well-established DSM-IV diagnosis of PDD-NOS should be given the diagnosis of autism spectrum disorder[8](https://www.autismspeaks.org/dsm-5-and-autism-frequently-asked-questions) |
| Prevalence effect | In a CDC ADDM 2008 data reanalysis, 81.2% of children meeting DSM-IV-TR ASD criteria also met DSM-5 criteria, giving 10/1,000 versus 11.3/1,000, a 9.1% reduction[9](https://sites.nationalacademies.org/cs/groups/dbassesite/documents/webpage/dbasse_173340.pdf) |
## Origin and definition
The category emerged from the effort to give the diagnostic manual a developmental orientation. In DSM-III-R (1987), a single autistic disorder and a subthreshold category were described, and the name of the latter was changed from atypical PDD to pervasive developmental disorder not otherwise specified.[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC3716827/) DSM-IV (1994) then listed PDD-NOS as one of the subtypes of pervasive developmental disorder, alongside autistic disorder, Asperger's disorder, Rett's disorder, and [childhood disintegrative disorder](https://www.edgepedia.org/childhood-disintegrative-disorder); the first three came to be referred to clinically as autism spectrum disorders.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC4929984/) • [11](https://www.oecd.org/content/dam/oecd/en/publications/reports/2026/03/policy-responses-to-rising-autism-diagnoses-in-childhood_68d7860e/08394255-en.pdf) The DSM-IV-TR code was 299.80, and the category explicitly included atypical autism.[12](https://portal.ct.gov/-/media/DPH/CYSHCN/Connecticut-Guidelines-for-a-Clinical-Diagnosis-of-Autism-Spectrum-Disorder.pdf)
The category was defined by exclusion rather than by criteria of its own. A review of differential diagnosis notes that no actual specific diagnostic criteria for PDD-NOS exist in the DSM-IV-TR; it served as a residual category for presentations that fell short of autistic disorder.[5](https://www.sciencedirect.com/science/article/abs/pii/S1750946706000080) In practice this made it a place for children who were clearly on the autism spectrum in clinical judgment but did not fit the other subtypes, and clinicians sometimes used it when a child's profile might shift between subtypes over development.[5](https://www.sciencedirect.com/science/article/abs/pii/S1750946706000080)
## Clinical characteristics
The most detailed description of the category comes from a [McMaster University](https://www.edgepedia.org/mcmaster-university) study that compared 216 children with autism, 33 with [Asperger syndrome](https://www.edgepedia.org/asperger-syndrome), and 21 with PDD-NOS, all diagnosed by expert clinicians, on measures of communication, daily living and social skills, IQ, age of language acquisition, and autistic symptoms.[6](https://pubmed.ncbi.nlm.nih.gov/14726723/) On level of functioning, the PDD-NOS children scored between the autism and Asperger syndrome groups. On symptoms, the PDD-NOS group had fewer autistic symptoms than both comparison groups, with the difference concentrated in repetitive stereotyped behaviors (chi2 = 11.06, p = .004).[6](https://pubmed.ncbi.nlm.nih.gov/14726723/)
The study divided the PDD-NOS children into three subgroups:
1. A high-functioning group (24%) who resembled those with Asperger syndrome but had transient language delay or mild cognitive impairment.
2. A subgroup resembling autism (24%) who had late age of onset, too severe cognitive delays, or were too young to potentially meet the full diagnostic criteria for autism.
3. A group (52%) who did not fulfill the criteria for autism because of fewer stereotyped and repetitive behaviors.[6](https://pubmed.ncbi.nlm.nih.gov/14726723/)
The authors concluded that with some revision to the diagnostic criteria, a more homogeneous atypical group with significant social-communication impairment but fewer repetitive behaviors could be differentiated from the more nonspecific remainder, which might improve diagnostic reliability and etiological research.[6](https://pubmed.ncbi.nlm.nih.gov/14726723/) A 2024 systematic review of comparisons with autistic disorder likewise argued for a clinical distinction between the two and suggested a multidimensional approach covering socialization, emotion lability, and psychotic symptoms at the margins of autism.[13](https://pubmed.ncbi.nlm.nih.gov/38173703/)
## Reliability problems
The residual definition produced weak diagnostic agreement. In an evaluation of the DSM-IV field trial data, three experienced raters made independent blind diagnoses from the same raw data (ADI-R, clinical notes, ADOS, IQ, Vineland scores, and the Autism Behavior Checklist). They differentiated autistic from non-PDD children and autistic from Asperger's disorder children with very good accuracy, with false negative error rates of 0.05 and 0.13 respectively, but their agreement on whether a child had PDD-NOS versus autism was poor.[7](https://mentalhealth.bmj.com/content/1/4/121) This unreliability was a central reason the category was difficult to study and was ultimately removed.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10217468/)
## Removal in DSM-5
DSM-5, published in May 2013, dissolved the pervasive developmental disorders category: autistic disorder, Asperger's disorder, childhood disintegrative disorder, and PDD-NOS were all collapsed into autism spectrum disorder, with severity specifiers replacing the subtypes.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC4929984/) • [14](https://acamh.onlinelibrary.wiley.com/doi/10.1111/j.1469-7610.2012.02614.x) The manual states that individuals with a well-established DSM-IV diagnosis of autistic disorder, Asperger's disorder, or PDD-NOS should be given the diagnosis of autism spectrum disorder, so existing diagnoses carry forward.[8](https://www.autismspeaks.org/dsm-5-and-autism-frequently-asked-questions)
The change had measurable effects on who qualifies. A re-analysis of the CDC Autism and Developmental Disabilities Monitoring Network 2008 survey year found that 81.2% of children with ASD under DSM-IV-TR also met DSM-5 criteria, producing a DSM-5-based prevalence of 10/1,000 against the reported 11.3/1,000 under DSM-IV-TR, a reduction of 9.1%; the removed, loosely defined PDD-NOS category was expected to increase the specificity of the ASD diagnosis.[9](https://sites.nationalacademies.org/cs/groups/dbassesite/documents/webpage/dbasse_173340.pdf) Commentators also warned of service consequences: because changing a PDD-NOS diagnosis to a Social Communication Disorder focused on language pragmatics could restrict eligibility for [Individuals with Disabilities Education Act](https://www.edgepedia.org/individuals-with-disabilities-education-act) programs, Early Intervention, and preschool special education.[4](https://pubmed.ncbi.nlm.nih.gov/23456348/)
The parallel international classification moved the same way.
## Related categories
Some proposals had argued for splitting conditions out of PDD-NOS rather than merging it. [Pathological demand avoidance](https://www.edgepedia.org/pathological-demand-avoidance) syndrome, described from a series of 150 cases with an equal sex ratio and discriminant function differences from classic autism and Asperger's syndrome, was proposed as a separate entity within the pervasive developmental disorders instead of being classed under PDD-NOS.[15](https://doi.org/10.1136/ADC.88.7.595) Conversely, follow-up of adults with childhood PDD-NOS or Asperger diagnoses found they experienced higher levels of autism-related problems as observed by parents, yet few met the formal ADOS criteria, illustrating the boundary problems the old category encoded.[16](https://link.springer.com/content/pdf/10.1007/s10803-020-04403-9.pdf)
## References
1. [What Are the Differences (and Similarities) Between Autism, Asperger Syndrome, and PDD-NOS? Hogrefe sample chapter](https://www.hogrefe.com/ch/shop/media/downloads/sample-reports/9780889373938_lese.pdf)
2. [The Diagnosis of "Pervasive Developmental Disorder Not Otherwise Specified": A Systematic Literature Review, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC10217468/)
3. [Update on diagnostic classification in autism, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC4929984/)
4. [Proposed changes to the APA diagnostic criteria for autism spectrum disorder: implications for young children and their families, PubMed](https://pubmed.ncbi.nlm.nih.gov/23456348/)
5. [Differential diagnosis of PDDNOS in children, ScienceDirect](https://www.sciencedirect.com/science/article/abs/pii/S1750946706000080)
6. [Walker DR et al. (2004). Specifying PDD-NOS: a comparison of PDD-NOS, Asperger syndrome, and autism. J Am Acad Child Adolesc Psychiatry 43(2):172-80](https://pubmed.ncbi.nlm.nih.gov/14726723/)
7. [DSM-IV criteria were reliable and accurate in differentiating PDD from non-PDD and autism from Asperger's disorder, Evidence Based Mental Health](https://mentalhealth.bmj.com/content/1/4/121)
8. [DSM-5 and autism: Frequently asked questions, Autism Speaks](https://www.autismspeaks.org/dsm-5-and-autism-frequently-asked-questions)
9. [Autism Spectrum Disorder Reclassified: A Second Look at the 1980s Utah/UCLA Autism Epidemiologic Study, PMC](https://sites.nationalacademies.org/cs/groups/dbassesite/documents/webpage/dbasse_173340.pdf)
10. [Autism in DSM-5: progress and challenges, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC3716827/)
11. [Policy Responses to Rising Autism Diagnoses in Childhood, OECD](https://www.oecd.org/content/dam/oecd/en/publications/reports/2026/03/policy-responses-to-rising-autism-diagnoses-in-childhood_68d7860e/08394255-en.pdf)
12. [299.80 Pervasive Developmental Disorder Not Otherwise Specified (Including Atypical Autism), DSM-IV-TR reprint, Connecticut DPH](https://portal.ct.gov/-/media/DPH/CYSHCN/Connecticut-Guidelines-for-a-Clinical-Diagnosis-of-Autism-Spectrum-Disorder.pdf)
13. [Investigating the borders of autism spectrum disorder: lessons from the former diagnosis of PDD-NOS, PubMed](https://pubmed.ncbi.nlm.nih.gov/38173703/)
14. [Ozonoff S (2012). Autism Spectrum Disorders in DSM-5: An historical perspective and the need for change, JCPP](https://acamh.onlinelibrary.wiley.com/doi/10.1111/j.1469-7610.2012.02614.x)
15. [Pathological demand avoidance syndrome: a necessary distinction within the pervasive developmental disorders, Archives of Disease in Childhood](https://doi.org/10.1136/ADC.88.7.595)
16. [Young adults with a previous clinical PDD-NOS or Asperger diagnosis, Journal of Autism and Developmental Disorders](https://link.springer.com/content/pdf/10.1007/s10803-020-04403-9.pdf)
17. [pubmed.ncbi.nlm.nih.gov](https://pubmed.ncbi.nlm.nih.gov/1483975/)
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*Topic: Encyclopedia › Life and health › Human health and medicine › Mental health › Neurodevelopmental conditions: ADHD, autism, and learning disorders*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license