[TexanFeller]

I think of ADHD and autism as brothers, or at least cousins. Lots of overlap, but not quite the same.

With the older concept and diagnosic criteria for autism there was less overlap. ADHD and autism used to be considered mutually exclusive diagnoses. Autism used to imply delays in speech and most people diagnosed also had significant intellectual disability. Autism is now a dramatically larger umbrella than it used to be with the last couple of DSM editions merging Aspergers and other conditions with it and making it not be mutually exclusive with ADHD. The shift in definitions makes autism extremely difficult to discuss in public because people have wildly different concepts of it depending on when they learned.

Side comment, merging Asperger's into autism was motivated in part by awareness of Hans Asperger's evil deeds and not wanting that association. It was also championed based on enabling help/protections given to autistics to folks with Aspergers as well, and maybe because being part of a larger and harder to ignore pool would help autistics with intellectual disabilities get more attention as well. So far I haven't seen a clear explanation of why it made sense in terms of better understanding the condition/difference, everyone that discusses it focuses on perceived potential social good.

[0olong]

A big factor was the defining feature of Asperger's being a lack of language delay, which turned out to be poorly correlated with life outcomes. The categories were also used very inconsistently - a lot of people, and some clinics, thought the Asperger's distinction implied far more than it did on paper, but not everyone went along with that.