One day while home sick about ten years ago I stumbled across and episode of Oprah. They were talking about use of the drug ecstasy and did something quite dramatic-they took MRI scans of several heavy users. One young woman who had cleaned up her act so to speak and was dressed really nice turned out to be shock. When they scanned her brain there were literally large holes in it. Where brain cells used to be. Brain cells apparently killed by ecstasy.
I think many young people view the drug as harmless. Well here is something even more damning-recent research indicates that a single dose can cause permanent memory loss. The study indicates that not only does a single session with ecstasy damage your memory but that the amount of drug consumed is irrelevant. Sounds like a substance you want to stay away from, especially if you're interested in physics. You're going to need those brain cells to learn quantum mechanics.
Read about it here.