I think that teenagers become drug addicts because of their curiosity and because they fall into bad company. One of the causes is lack of responsibility. The other reason may be their wish to raise popularity in the circle of their contacts. Teenagers can`t imagine all  consiquences of this bad habbit. The result of drug addiction may be blood poisoning, dependence, depression, overdosage. Drugs may lead people to crime. Relatives, as well as friends, may abandon you.   

I think teens begin to take drugs because of their curiocity or because getting in a bad company. Also, maybe, because they want to become more popular in some society. Teens can't imagine all the difficulties. Drugs can cause: blood infection, addiction, depression, overdose. People can become criminals beecause of taking drugs. Your relatives can refuse talking to you, as well as your friends.
Надеюсь, всё правильно :)