Comment by oxymoron

I think it’s at least relevant to note that a lot of things relating to autism was completely redefined in DSM-V. DSM-IV had many different diagnosis such as classic autism, autism spectrum disorder, aspergers and PDD-NOS (Pervasive Developmental Disorder - Not Otherwise Specified). All of those was merged into a single diagnosis titled ”Autism Spectrum Disorder”, where the criterias are communication difficulties and stereotypical behavior. My understanding is that this was mostly due to poor diagnosis stability with the prior set of diagnosis. It seems at least plausible that this general simplification of diagnosis criteria has contributed to an increase in the number of diagnosis. (It’s also worth remembering that any comparison over time has to bundle all of the previously distinct diagnosis to come up with an apples-to-apples comparison.)