The term Pervasive Developmental Disorder (PDD) was once used to refer to a category of developmental delays that included autism and four similar disorders, and was defined as the umbrella that these five disorders fell under:
- Asperger syndrome
- Rett syndrome
- Childhood disintegrative disorder
- Pervasive developmental disorder not otherwise specified (PDD-NOS)
In 2013, the 5th edition of the Diagnostic and Statistical Manual (DSM) of Mental Disorders – the primary diagnostic criteria resource psychiatric professionals use – was released. In the DSM-5 the old definitions for Pervasive Developmental Disorder (PDD) became obsolete.
In the DSM-5, all five of the separate categories were grouped into the new definition for autism spectrum disorder. As a practical matter, this eliminated the need for the term “pervasive developmental disorder” to describe them—now, autism spectrum disorder means the same thing.
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This is part of the reason why the term PDD has become a source of some confusion – and the reason it has largely fallen out of use.
Still, you may hear autism spectrum disorder (ASD) referred to as part of a larger class of developmental delays called pervasive developmental disorders. You may also hear of people diagnosed with pervasive developmental disorders not otherwise specified (PDD-NOS) … an entirely different class of diagnoses once considered separate from ASD. But the term PDD-NOS has become obsolete too as it now falls under autism spectrum disorder.
Not surprisingly, there is a considerable amount of confusion around the term PDD.
The problem is that clinicians still sometimes use the term PDD, but they don’t always use it consistently. Some still stick to the DSM-4 definition while others use the term more or less interchangeably with “ASD,“ in line with how the DSM-5 defines it.
Pervasive Developmental Disorder Is Still Widely Used Despite Being Unofficial
Not all clinicians have immediately adopted the DSM-5 definitions, because they believe that the DSM-4 categories were more descriptive. Others use the DSM-5 criteria clinically, but continue to use some of the old nomenclature from DSM-4 out of habit or as shorthand for categories that DSM-5 does not explicitly define.
Making matters even more complicated, medical professionals and many insurers use the International Statistical Classification of Diseases and Related Health Problems, or ICD-10, for diagnoses. The ICD-10 continues to include a classification for pervasive developmental disorder, unspecified, although it does not contain detailed criteria for providing a diagnosis.
That is in keeping with the original use of PDD-NOS, however, which was essentially a catch-all diagnosis for individuals who exhibited some autistic symptoms but did not meet the previously more stringent criteria for a definitive autism diagnosis. Additionally, because of the sometimes gradual onset of autism symptoms in toddlers, clinicians sometimes preferred to makes a diagnosis of PDD-NOS in cases where there remained some question as to whether or not full-blown autism would manifest in younger patients.
So, although PDD and PDD-NOS were (and still are, by some professionals) sometimes used interchangeably, they did not refer to the same thing. Today, both are essentially absorbed into the broader definition of autism spectrum disorder.