Autism increased because they changed the definition of autism and Federal money flowed into education for students who were classified as having it.
If they change the definition of AN and hand out money for it, AN's will skyrocket as well.
Autism showed an apparently-increased incidence in the UK where I live yet no additional money had flowed into our education system. (we don't yet do federal although Europe might like us to be part of that federation ) There's still a dearth of special needs provision in the UK for autistic kids and others with different learning difficulties.
The provision of appropriate funding remains a pipe dream.
What they did here was to decide that every child that isn't exactly the same as every other child is now autistic. Some of those kids are truly autistic. Other kids have some special need that is not, IMO, truly autism. But, they made everything "autism" since that is where the money is. Most of the kids, IMO, are actually perfectly normal and there is nothing "wrong" with them. Since a kid who is perfectly normal, but not getting straight A' in all of their classes doesn't seem to satisfy the schools and their endless lust for public funding, or the parent's who don't want to accept that their kid is just average intelligence or maybe just not that fascinated with school to engage their studies enough to get perfect scores on everything they do, you see them all "diagnosed" with autism.
It used to "ADHD", then it was "autism", and I've noticed lately that many are now classified as both. It's a real mess with no end in sight. When I think back about all of the kids in my class when I was growing up, including me, and ponder what these experts would have done with them if they had the chance back then, it blows my mind.
Bill Gates never graduated college, many of our greatest leaders were brawlers and drop-outs, even involved in criminal activity. Now, anybody like that is classified as "something", medicated and/or put in special programs that all but ensure they will never accel at much of anything.
My buddy's daughter is a great example. She is brilliant, but socially and physically awkward. He's very sensitive about it, so I don't know what name had been assigned to her "condition" because I never wanted to ask him about it directly, but I know she was considered something along the "autism spectrum". Come to find out, that a different medical Dr (as opposed to the school psychologists etc) just sent her for an MRI which revealed some type of cysts on her brain. All of these years with special this and that to teach her how to be "autistic" and she has had a serious brain tumor condition that she could have died from if it weren't for them finally getting to the right professional that actually knows a thing or two about what he is doing.