Well - environmental toxins are at the bottom of a lot of it.   It's true there are different genes that can be involved and so the way in which it is expressed differs, however, I know people who have kids who were hyper, distracted, too intensely mono-focused or always anxious, and the approach I outlined above worked for them.   MTHFR genetic defects seem to underlie some of it.    Heat shock protein defects are also a big issue.

With autism, there are similar issues in many (not all) cases, however, they tend to be far more extensive and more digging into the root causes needs to be done to make major breakthroughs.