Living in Europe, my perception (AKA: anecdotal / unscientific / non-measured) is that most of the ADHD-diagnosed people I know live in the US, while I only know one European person in my network who received similar diagnosis from a professional psychiatrist. Counterintuitively, I know way more European people than Americans, which makes my perception feel even more skewed. I very well know that my sample(ing method…
I have also known a lot of people who tend to self-diagnose problems that I suspect they don't really have and then talk about them a lot (such as ADHD). They're usually the people who are fixated on vaccines and 5G as the cause of many health problems, but they typically won't have much interaction with "establishment" doctors on these issues. It's my impression that this is more common in the US than Europe, but it's a distinct issue. Not sure if some of that is mixed in to your observations?