Why PDD-NOS Is No Longer a Valid Diagnosis

Prior to 2013, there were five separate diagnoses that existed on the autism spectrum, one of which was called pervasive developmental disorder not otherwise specified (PDD-NOS). PDD-NOS was the diagnosis given to children who didn't fully fit the criteria for one of the other autism diagnoses in use at the time—which included Asperger's syndrome, childhood disintegration disorder, Rett syndome, and pervasive developmental disorder (PDD)—but still had some symptoms consistent with autism.

All of these subtypes were folded into a single diagnosis of autism spectrum disorder upon the 2013 publication of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), with the severity of the disorder defined by a level of 1, 2, or 3.

Symptoms of PDD-NOS

As with all types of ASD, PDD-NOS is characterized by difficulties with social communication and interaction, as well as engaging in restrictive or repetitive behaviors, including:

• Making poor or no eye contact
• Having a hard time expressing feelings or emotions, or not being aware of the others' feelings
• Trouble interpreting nonverbal cues, such as facial expressions or body language
• Repetitive behaviors, such as rocking back and forth or repeating specific words or phrases
• Being dependent on specific routines and being upset when there are changes to it
• Being over- or under-sensitive to sensory stimulation, such as noise and light
• Having narrow and highly focused interests in specific topics or hobbies

Children with PDD-NOS, like those with any form of autism, can have a wide range of intellectual and verbal abilities—or they may have severe symptoms when it comes to social communication, for example, but don't exhibit restricted, repetitive behaviors.

Diagnostic Challenges

PDD-NOS was essentially a diagnosis of exclusion, a "catchall" term used for people who were on the autism spectrum but didn't fully meet the criteria for another autistic disorder in use at the time.

In addition, the DSM-IV stated that a diagnosis of PPD-NOS could only be given if four other disorders not on the autism spectrum were ruled out. These included schizophrenia, schizotypal personality disorder, or avoidant personality disorder.

While PDD-NOS did provide a diagnostic option for doctors looking at children who had a range of differences that didn't seem to fit any particular category, the category was so general and so vague that it told parents, therapists, and teachers very little. Unlike the now-defunct Asperger's syndrome category, which was another term for "high-functioning autism," PDD-NOS could mean virtually anything. A new diagnosis introduced in the DSM-5, social communication disorder, may become a similar catchall category.