On Sunday night, December 18, 2011, the Discovery Channel aired a program on "Your Body on Drugs" through its Curiosity series. It showed four drug users, one who uses marijuana, another who uses meth, a third who uses cocaine and a fourth who uses heroin, go through four different situations while on their respective drugs. The program showed how each user reacted in each situation and gave some lessons on how each drug affects the body's physiology. This program is well worth watching. Look for repeats of it on your TV.
As a companion to the show, Discovery Channel has posted a web page on information about drugs at:
This web page is also well worth looking over.