Gentlemen, my addition to the discussion: most of the reason that intelligent folks like on IE cannot rapidly come to a clarity on this is that the medical psychology community doesn't know what it is talking about. This community tries hard but it makes the same labeling errors all the time. Because it cannot simply understand the complexity of the brain [either chemically or structurally] it is faced with issues of diagnosis which it cannot handle. Thus it makes up collective junk-words to cover a wide spread of underlying problems.
These junk words [ex. depression, hyperactivity, PTSD, schizophrenia, even "epilepsy" spreads out over many different things] though they mean well, are merely rough descriptors of surface evaluated behavior and not fundamental causality. But they slowly take on a larger life of their own as if they really mean something. Thus hyperactivity [a behavioral observation and judgement] becomes such a "thing" that it becomes casually accepted and gets its own fancier formal name, ADHD.
Child psychologists who manage to keep their scientific open-minded objectivity have known at least since the seventies [when I had to teach some of this stuff in a human biology class] that "hyperactivity" seemed occasionally related to a real brain chemistry imbalance [maybe "purely biochemical" via a genetic flaw, or maybe structural in the neurons/synapses] and could produce the seriously distracted "off-the-walls" child mentioned in the thread. This would be a true problem and not to be laughed off.
On the other hand, those same researchers [inspired by the already growing horror show of excess Ritalin use] recognized that the tendency was gaining to assess every "active" kid as "hyperactive" and go with a convenient "solution". This early excess wave of diagnosis was found to be due to bad diagnosis in the school system. It quieted classrooms down and mainly-ignorant parents went along --- their homes got quieter too.
The improper use of Ritalin [not the PROPER cases] had the following educational effects: it DID show a marginal increase in the learning of rote learning tasks like brute memorization and repetition tasks. But it markedly suppressed "higher" learning skills and creativity.
That some brains "go too fast" [for whatever reason] is to be expected --- everything in biology [height, build, bone strength ...] gets genetically thrown out there on a Bell-shaped curve. For the most part you want to be near the middle of that curve. Both "wings" usually are dangerous to function if not survival. Some kids are going to be born "going to fast"... BUT THEY WILL BE RARE. The fact that we are happy to diagnose all manner of kids as ADHD and drug them out of our own convenience is a national shame.
In those early studies kids were put on Ritalin when a glass of milk in the morning or not living beneath the El-Train wouldn't have "cured" them.