Weirdly I feel it is both over and under diagnosed.
I have a mental health condition I have suffered with my whole adult life. It impacts my quality of life quite a lot.
I have been to the GP countless times, been to private and NHS therapy, a private psychologist. I tried all the suggestions to help myself.
Eventually after about 13 years of struggling I did get a diagnosis and lovely validation from an amazing professional and he was quite upset on my behalf I hadn't been helped sooner.
I wasn't exactly begging for a diagnosis, and I am not a pushy personality in medical settings, so that may have had an impact.
But then I also know a lot of people diagnosed very, very quickly with Autism and ADHD including my own sister (who now sells her ADHD meds).
It has been eye opening getting back into working in school settings and seeing how many parents are adamant their child is SEN for what are very normal development stages and challenges.
(not denying some of the parents are completely valid).
So in my experience you have to be very pushy to get a diagnosis. I wonder how many do get a diagnosis because they were so adamant about it.
I've also heard in person and seen on social media people being angry they weren't given a diagnosis and they have been validated by comments that a self diagnosis is just as valid.
Whilst we know our own bodies and minds, I don't think the validity of a professional diagnosis should be ignored, especially when there are clearly people who abuse the system.
And a lot of more quiet people fall through the cracks and never get help.