Specifying PDD-NOS: A Comparison of PDD-NOS,
Asperger Syndrome, and Autism

Walker D, Thompson A, Zwaigenbaum , Goldberg J, Bryson S, Mahoney, W, Strawbridge C, Szatmari P
Department of Psychiatry and Behavioural Neurosciences,
McMaster University, Hamilton, Ontario

Abstract: J Am Acad Child Adolesc Psychiatry 43:2 2004

Findings

In diagnosing children with autism spectrum disorders (ASD), doctors will often assign the category of PDD-NOS (pervasive developmental disorders-not otherwise specified) to those who don’t match a specific diagnosis of autism or Asperger syndrome (AS); however, the category of PDD-NOS doesn’t have specific criteria and is often used as a diagnosis of exclusion. The term PDD-NOS can be misleading and ambiguous to parents and doctors. To better understand what clinical characteristics distinguish children diagnosed with PDD-NOS from other children with ASDs , Dr. Darlene Walker and her colleagues compared 216 children with autism, 33 with Asperger syndrome, and 21 children diagnosed with PDD-NOS. Children were studied for level of functioning (communication, daily living, and social skills, IQ, and age of first language) and symptoms of autism (impaired communication, reciprocal social interaction, and repetitive and stereotyped activities). They found that for level of functioning, the PDD-NOS children had scores between those of autism and AS. However, PDD-NOS children had fewer autistic symptoms (particularly repetitive behaviors) than autism and AS individuals. Further analyses suggested that children with PDD-NOS can be divided into three groups: (1) high-functioning, resembling AS, but with transient language delay or mild cognitive impairment, (2) those resembling autistic children but had late onset of cognitive delay or mild cognitive impairment, (3) a group not fulfilling criteria for autism due to fewer repetitive behaviors.

Conclusions

Children diagnosed with PDD-NOS comprise a heterogeneous group. On average they are higher functioning compared to children with autism, have more delayed language than children with AS, and have fewer repetitive behaviors than either group. The authors suggest that changing slightly the criteria for both AS and atypical autism may lead to a more accurate classification of these children. The term PDD-NOS should then be reserved for children for whom there is not enough clinical information (young age, poor documentation, etc.) to make a more specific diagnosis. The result will be a more reliable diagnoses and more accurate studies on the causes of ASDs.