ADHD is the same thing for many people. It’s an infant driven to distraction because of “problems in the environment”. Well maybe there are congenital cases, but there are others that aren’t, and there’s no money in the root cause analysis.
It’s a brain development disorder. That means the brain doesn’t develop the same. Not just a baby “driven to distraction”. Genes and environment. For example it’s more common in premature babies. Plenty of past and ongoing research