Oh, for autism? They broadened the definition of autism around 1993.
Prior it was spinning plates and stimming.
After it included Aspergers and many symptoms that previously were lumped under “nerd” or in a generalized anxiety category.
Also, with a lot of money put into research over the past decade, better screening methods are available, allowing more cases to be discovered and help provided more quickly.
So, I don’t think the increase in autism can be linked to any chemical agent.
Personally? I think of high functioning autism is a personality trait but with the diagnosis, doors open up for assistance as schools are not geared around certain personality types. I think this is also true with ADHD. They’re real but they’re only a problem because of a lack of understanding of personalities that sit outside the bell curve.