I heard a very sobering story from a student once (I worked at a remote school where weed usage was so common that it was practically discussed in the hallway). Where he came from, smoking marijuana was a family tradition. Everyone did it. And if you refused it, you were refusing family and incurring a very real risk of getting ostracized. Every drug user typically has a "community" that tries to keep them hooked and part of the group. But it's tough when that community is your very own family.