The main reason that autism, dyslexia, dyspraxia, ADHD, and eating disorders were not around 40 p[us years ago is quite simply that they were not recognised or even identified at the time as specific problems at the time..
We were the awkward, difficult, bullied children who some teachers had it in for, who were constantly in trouble for our clumsiness or poor handwriting, or being unable to sit still or concentrate.
I cannot count the number of times I was made to rewrite my homework because of my handwriting, or got accused of not making an effort etc etc. In fact I am dyspraxic and possibly have ADHD,
Dyspraxia was not recognised as a specific syndrome until the 1980s. I was fortunate to be recognised and diagnosed with the problem quite early on, when I was in my 40s, but how much better my school days would have been if the problem had been recognised and understood then.
I am sure there are many other GN members who will have had similar experiences to mine.