The medical consensus after multiple enquiries in the UK has come to:
1. The rate of diagnosis is far too low (the evidence of this being we're catching people as adults who should've been caught as children).
2. Our diagnostic criteria aren't inclusive enough (we have historically missed inattentive presenting ADHD, we have historically missed ADHD presenting in women)
These results are politically unpalatable so the enquiry is I think currently being run for the third time, but signs point to ADHD overdiagnosis being a hoax/fake news/whatever you call it.