In this piece Pastor John Piper, founder and teacher of desiringGod.org, gives the reasons he believes Christians should avoid recreational marijuana use. He begins:
Marijuana is ordinarily used as a mood-altering, mind-altering drug. The aim is to create a kind of euphoria. The effects vary widely from person to person. All you have to do is Google, “What does Marijuana feel like?” People don’t smoke it to get unhappy. It produces a temporary state that is felt to be better than ordinary life. That’s why it’s called a “high” and not a low.
So the first comparison one might be inclined to make is with caffeine. Most people drink coffee because caffeine has a pleasant effect. But there is a difference. Marijuana temporarily impairs the reliable processing of surrounding reality. Caffeine ordinarily sharpens that processing.