There is likely a selection biased. A lot of mental health issues and quirks have genetic components. If you have an issue, it's FAR more likely your family has issues.
We also tend to be attracted to like minded individuals. My partner tried to tell me I was normal, until I was diagnosed. They were diagnosed a few years later. It turned out most of their friends were neurodiverse too. They were rating themselves (and me) against a bunch of fellow weirdos!
A lot of the problems have always been there. They were just seen as personal failings and hidden. Now we know that they have an adjustable chemical component that can be used to treat them. That, combined with more people being open about issues has created the spike.