It's especially important to remember how new these diagnoses are.
The first person to be diagnosed with Autism died just a few weeks ago!
And it wasn't until 1968 that ADHD was added to the DSM.
Even after something is added to the DSM, it can take time for that classification to gain awareness and acceptance.
I was diagnosed with ADHD in 1984, and I remember even as a kid people how much "skepticism" it was met with.
@serge @Garwboy
although the word "autism" wasn't used, it appears that the dis order was known in , at least, the early 1800s.
https://beyondthespectrummovie.com/a-history-of-autism/
see also here, autism in the mid 1800s
https://www.smithsonianmag.com/science-nature/early-history-autism-america-180957684/
and this notes how part of the increase in diagnosis is due to closure of "mental hospitals"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3757918/
@serge @Garwboy
although the word "autism" wasn't used, it appears that the dis order was known in , at least, the early 1800s.
https://beyondthespectrummovie.com/a-history-of-autism/
see also here, autism in the mid 1800s
https://www.smithsonianmag.com/science-nature/early-history-autism-america-180957684/