I'm not disagreeing about over-prescription by any means. It's a serious problem. I'm just disagreeing about the particular qualities of one medication, Ritalin. Not all medications are inherently and utterly evil in all cases. We can all agree that it's idiotic to put penicillin on your eggs every morning, but penicillin still does have some valid uses. The presence of bathwater does not rule out the possibility of a baby.
So. Ritalin is not even remotely a depressant. What it does depends on brain chemistry; it's a mild stimulant for most people, but for those with certain vagaries of brain chemistry it behaves quite differently. Those "certain vagaries of brain chemistry" are what's known as ADHD. People in that state find it difficult, in varying degrees, to focus on anything. They often want to focus, but they can't. You can tell them to "just do it", but that's like telling somebody to stop stuttering. People don't choose to be this way. Ritalin enables them to focus in many cases (not all; psychopharmacology is not an exact science, even by the loose standards of the medical profession). It enables them to decide for themselves what they're going to think about, rather than having their thoughts flit about uncontrollably. The president of the company where I work is on Ritalin, and he is damn near the least sedated person I've ever met. If that guy is on Ritalin, then most of what you hear about Ritalin is pure fantasy.
According to a psychologist I know, a big problem with giving Ritalin to little kids is that it affects their growth and development. It can be a very bad idea if not handled well, and not everybody who prescribes the stuff does handle it well. This, not the "depressant" myth, is a genuine cause for concern. Furthermore, it is often prescribed without reason, which is a Bad Thing not only because of the growth'n'development issue, but also for all the usual reasons: It is a drug and should approached with fear and trembling when you give it to kids (or any one, but kids especially), and it has undesirable effects on people who don't have the condition which it addresses. Ritalin, whatever benefits it may occasionally offer, should no more be over-prescribed than antibiotics or anything else.
I am not a psychopharmacologist, nor do I play one on TV.