Give or take a few years. There are a number of subtle developmental differences between individuals. Not saying the doc is correct on diagnosing a 4 year old with ADHD, as some docs still like to jump the gun on that. However, so long as the diagnosis results in evidence-based treatments that do not involve drugs, it may still be beneficial. I say this as a 44 year old who was not diagnosed until 41, and that was after almost 10 years of trying to explain to docs what was happening to me, and the hell that it made my life. From my perspective, it becomes a question of which is worse; diagnosing and treating too early (sans drugs) or trying to fix a broken adult set in their ways?