theyres some prescription anti-depressants and anti anxiety meds that mess around and change the amounts of certain chemicals in your body, i would think that it would change the high. a friend of mine is on some sort of med like that and he trips out when he smokes, even a little.

maybe it has something to do with MAOI's i know they affect how alot of drugs work on you.

oh and "uppers" doesnt only reffer to pills, coke, caffine, cigs and pretty much anything that wakes you UP or gives you energy i would consider an UPper

weed on the other hand is a downer like heroin and alcohol