Hi
I'm on the autism spectrum. It's a different brain design that happens before birth, from what they're seeing. There's no clue whatsoever, from anyone, how it happens. Lots of theories but no answers. There can indeed be a genetic link but sometimes/fairly often there isn't.
Yup, Ed Psychs are not able to diagnose, though some point people in the right direction.
Most adults on the autism spectrum have never had a diagnosis. It was only really made available from the mid 1990s, and for women it's really been the last five years or so. Why? Because they thought it was a condition that was always very severe, almost always affected boys, etc. And so they designed questionnaires for professionals that asked questions that boys would answer yes to (but girls probably wouldn't) e.g. "do you collect information about trains?" (er, no...women tend to collect shoes, handbags, ornaments etc...)
Thus, most women still don't have a diagnosis and don't have a clue that they're on the spectrum.
Some, when realising it's a possibility, ask their GP to refer them for diagnosis. Expect a huge waiting list. Or, if there's money, they might go to a private specialist (the National Autistic Society can point people in the right direction for this).
Is a diagnosis worth it for adults? It can be but it's a very personal choice. For me it was great, because it meant there were reasons why I'd found things so hard. And I learned ways to do things better or help myself more.
If you have a child on the autism spectrum, (as I do), having a parent who's also on the autism spectrum can be very handy, because we can show them how we've coped so far. It's certainly not a greater or lesser problem than having a parent who isn't autistic (though some of us need a bit of more specialised help with parenting skills).
Have a large cuppa. Much to think about. But there are so many good people in this world who have forms of autism.