The Difference Between Aspergers and PDD-NOS


My 7-year-old son has been diagnosed with ADHD. The pediatrician also thinks that he may have Aspergers or Pervasive developmental disorder not otherwise specified. After researching the two diagnoses, I see that they are very similar. What type of testing can I have done to determine what kind of help my son needs?


Like Autism and Aspergers, Pervasive developmental disorder not otherwise specified (PDD-NOS) is one of the five subtypes of the Autism Spectrum Disorders. Children diagnosed with PDD-NOS will have less social impairment than a youngster with Autism or Aspergers.

The Autism Spectrum Disorders are:

1. Pervasive developmental disorder not otherwise specified
2. Autism
3. Asperger syndrome
4. Rett syndrome
5. Childhood disintegrative disorder

To confuse matters, there is a division among therapists on the use of the term Pervasive Developmental Disorder (PDD), which is the same thing as Autism Spectrum Disorder (ASD). Many use the term PDD as a short way of saying PDD-NOS. Others use the general category label of PDD because they are hesitant to diagnose very young kids with a specific type of PDD (e.g., Autism). Both approaches contribute to confusion about the term, because the term PDD actually refers to a category of disorders and is not a diagnostic label.

PDD is not itself a diagnosis, while PDD-NOS is. To further complicate the issue, PDD-NOS can also be referred to as “atypical personality development,” “atypical PDD,” or “atypical Autism.”

Some clinicians use PDD-NOS as a "temporary" diagnosis for youngsters under the age of 5, when for whatever reason there is a reluctance to diagnose Autism. There are several justifications for this. Very young kids have limited social interaction and communication skills to begin with, thus it can be tricky to diagnose milder cases of Autism in a toddler. The unspoken assumption is that by the age of 5, unusual behaviors will either resolve or develop into diagnosable Autism.

Because of the "NOS" (i.e., not otherwise specified), it is hard to describe what PDD-NOS is, other than its being an Autism Spectrum Disorder (ASD). Some children diagnosed with PDD-NOS are close to having Aspergers, but do not quite fit the profile. Others have near full-blown Autism, but without some of its symptoms. The field of psychology is considering creating several subclasses within PDD-NOS.

To confirm the diagnosis, continue to consult with your doctor and get a referral to either a neurologist or child and adolescent psychiatrist to figure out exactly what is going on with your child. Once you have a definitive answer, you can then check for resources in your local area. Each U.S. state has different resources tied-in with the local schools. Your doctor should be able to point you in the right direction. If not, the local school district should have some referrals for you.

The Aspergers Comprehensive Handbook


  1. This was a great question to ask! My son was recently diagnosed as PDD-NOS and I had somehow gotten the clue that he was considered to be on the mild side of autism but no one was really clear about what that meant. I kept hearing how Aspergers was also mild and was confused about what the difference was also. I am not so sure my questions are completely answered after this but it did help!

  2. I have a two yr old. So far the Dx we have is SID, PDD-NOS, and vision impairment. There are things that he does that are red flags for spectrum disorders, yet there are other things he does that are not. He is social, does not have speech delays, and other things. I'm not sure what to do. All his therapists say he does not have autism but do not know what he does have. Every time he is evaluated but someone it is done in a therapy setting, and since he has been in therapy since a year he knows what to do so they are not getting an accurate feel of how he acts. I feel like no one is listening to me. I wish I could video tape how he acts at home and in certain situations. Did anyone else run in to this problem? Any words of wisdom?

  3. I often wonder if we are the only parents of an aspie-ish PDD-NOS son who has learning disabilities, instead of academic gifts. Have you covered that scenario? We seem doubly burdened because the LD brings in so many school challenges that most aspies sail through. Math and writing especially.

  4. I've discovered over the years that some PDD-NOS kids are really AS/ADHD kids. It's possible that's what's going on in your case (perhaps a second opinion from a diagnostician who specializes in Aspergers would be helpful). PDD-NOS may be thought of as “subthreshold autism," or a diagnosis one can give a person who has “atypical symptomatology.” In other words, when someone has autistic characteristics but some of their symptoms are mild, or they have symptoms in one area (like social deficits), but none in another key area (like restricted, repetitive behaviors), they may be given the PDD-NOS label. Researchers have found that those with PDD-NOS could be placed in one of three very different subgroups:

    A high-functioning group (24%) who resembled people with Asperger syndrome but had transient language delay or mild cognitive impairment (such that they could not receive the Asperger diagnosis which requires no speech or cognitive delay).

    A group (24%) who resembled people with autism but who had a late age of onset, or otherwise did not meet the criteria for autism.

    A group (52%) who were autistic-like, but displayed fewer stereotyped and repetitive behaviors.

    I'm not sure I answered your question, but there you go...


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