Information on PDD-NOS, an Autism Spectrum Disorder


The classification and diagnosis of Autism Spectrum Disorders, most of which are also known as Pervasive Developmental Disorders, is typified by this disorder. Pervasive Developmental Disorder - Not Otherwise Specified is usually shortened to PDD-NOS, and is a ‘sub threshold’ condition in which some — but not all — features of Autism or another explicitly identified Pervasive Developmental Disorder are identified.


pdd-nos and terminology

PDD-NOS is often incorrectly referred to as simply “PDD.” The term PDD refers to the class of conditions to which Autism belongs. PDD is not itself a diagnosis, while PDD-NOS is a diagnosis. To further complicate the issue, PDD-NOS can also be referred to as “atypical personality development,” “atypical PDD,” or “atypical Autism”.


pdd-nos and diagnosis

PDD-NOS is included in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) to encompass cases where there is marked impairment of social interaction, communication, and/or stereotyped behavior patterns or interest, but when full features for Autism or another explicitly defined PDD are not met. Typically, the symptoms should be recognizable before a child is 3 years old. Although a toddler's behaviors might seem to fit the criteria, they also might just be part of a youngster's developing personality.

It should be emphasized that this ‘’sub threshold’’ category is thus defined implicitly, that is, no specific guidelines for diagnosis are provided. While deficits in peer relations and unusual sensitivities are typically noted, social skills are less impaired than in classical Autism. The lack of definition for this relatively heterogeneous group of children presents problems for research on this condition. The limited available evidence suggest that children with PDD-NOS probably come to professional attention rather later than is the case with autistic children, and that intellectual deficits are less common.


Case Illustration of pdd-nos

Leslie was the oldest of two children. She was noted to be a difficult baby who was not easy to console but whose motor and communicative development seemed appropriate. She was socially related and sometimes enjoyed social interaction but was easily over stimulated. She was noted to exhibit some unusual sensitivities to aspects of the environment and at times of excitement exhibited some hand flapping.


Her parents sought evaluation when she was four years of age because of difficulties in nursery school. Leslie was noted to have problems with peer interaction. She was often preoccupied with possible adverse events. At evaluation she was noted to have both communicative and cognitive functions within the normal range. Although differential social relatedness was present, Leslie had difficulty using her parents as sources of support and comfort.


Behavioral rigidity was noted, as was a tendency to impose routines on social interaction. Subsequently Leslie was enrolled in a therapeutic nursery school where she made significant gains in social skills. Subsequently she was placed in a transitional kindergarten and did well academically, although problems in peer interaction and unusual affective responses persisted. As an adolescent she describes herself as a `loner’ who has difficulties with social interaction and who tends to enjoy solitary activities.


click this button to shut the fact sheet

Click here for the full range of Asperger's and Autism fact sheets at
This autism fact sheet is licensed under the GNU Free Documentation. It is derivative of an Autism and Asperger's syndrome-related articles at

Pervasive Developmental Disorder - Not Otherwise Specified is an Autism Spectrum Disorder