[floxy]

>Looking at the rates of ADHD diagnosis worldwide, it is clear that someone is getting it wrong

Isn't the usual answer something like:

"People with ADHD-like characteristics are restless and impulsive, therefore more likely to decide to strike out on big new adventures. Like emigrating to an exciting new country. So the U.S. has been an ADHD magnet since before its founding, leading to a much higher prevalence / diagnosis than most other parts of the world. And since ADHD is hereditary, it gets passed down the generations, sustaining the imbalance with the rest of the world. And/or maybe there is an amplification effect where in most populations the ADHD genes stay diluted in the gene pool, since it is not a common occurrence, and people with ADHD generally had kids with non-ADHD people. But at certain base rates, the ADHD people start having children with each other, intensify the effects."