Jon Brock discusses PDD-NOS at Thinking Person's Guide to Autism. Don't know what PDD-NOS is? Read on, even if you think you know what it is you should give this a read.
PDD-NOS and DSM5
Some cases of autism are obvious. Anyone who knew anything about autism would agree that the child or adult in question was autistic. Other cases are less clear cut. Indeed, the term "autism spectrum" implies the existence of a continuum that fades gradually into what we think of as the "normal" population.
Somewhere a line has to be drawn and where exactly we choose to draw that line defines what we mean by autism. It determines who is eligible to take part in autism-related research and this in turn influences the development of theories of autism. Eventually, this feeds back to our evolving definitions and cut-offs for autism. Most importantly when it comes to immediate real-world consequences, the diagnostic boundaries specify who is labeled "autistic" and, ultimately, who gains access to interventions and support.
In the absence of reliable biological markers or break points in the continuum, diagnoses are made by checklist. Tick enough boxes and you get a diagnosis of "autistic disorder" or "Asperger's disorder". Tick fewer boxes or the "wrong" combination of boxes and you're not considered autistic. You may, however, qualify for the mysterious diagnosis of PDD-NOS - "Pervasive Developmental Disorder -Not Otherwise Specified". Read more.