Drugs are known to be terribly addicting, especially to teens. When put on regular highs, or drugged by someone else, you can sufffert the consequenses, which more than often means death.
When taking drugs, it's another gateway to diseases you may have when you're an adult The effects that drugs take on your body could stay there for the rest of your life.
Drugs can also be the root of disobidient tendencies, sneaking out, going to parties, lying very often to a guardian/teachers. It can leade teens down rabbit holes.