My life is having fact and reference.

The idea of caffeine having the opposite effect is not a difficult one to grasp -- caffeine is a stimulant, albeit a mild one, and as such acts something like Ritalin would in an individual with AD/HD.

I notice that whenever I eat or drink something with a fairly small amount of caffeine (80-100mg or so), it pretty much puts me to sleep after a short burst of attentiveness -- this may be due to the amount. More than that, and it actually does help me to focus. If I really need to, I'll have a couple espressos to focus. I rarely do that, though, as I am not the kind of person who self-medicates (Warning, the following is opinion: in fact, I am quite opposed to the rampant prescription of pharmaceuticals in cases where things could be handled in other ways, or at least with less dosage).

There are also a *ton* of studies available by searching PubMed on the efficacy of stimulant medication w/ regards to AD/HD. An interesting one on first glance is SUNY Buffalo's study on kids in a summer camp. In this study, the role of dopamine and norepinephrine in AD/HD is reviewed.

If these are to be believed (that is to say, one comes to the conclusion that stimulants do indeed work in the suggested way), then it's not hard to see why caffeine works on you and I in the way that it does.

If you want the full-text articles of those, you can send me a private message thing and I'll try to grab it from my uni's database when I check those messages -- or if you have a scholarly journal search tool available, plug in the data and see what comes up.