While "experimentation" during the teenage years can be a fairly normal rite of adolescence, it can also, in some cases, mean there is something very wrong.
If your child is getting drunk or high on drugs on a regular basis, or you notice your prescription drugs have gone missing (check them!), don't ignore it. Yes, it could be a case of teenage rebellion that uneventfully runs its course. It could also be a sign of depression and self-destructive tendencies and a blaring cry for help. If it's the latter, your teen needs you to step in.
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