Has your son or daughter drawn pot leaves or bottles of beer on his or her notebook? It is actually a sign of "preoccupation" and "infatuation", in the same way that it was when you wrote the initials of you and your boy/girlfriend inside the heart on your notebook when you were a kid. Remember? or was I the only one that did that? 

Kids who end up addicted start out by loving to get high. So, as a parent we need to look for some clues, that are not so obvious, doodles of pot may be that very sign.