In this day and age, being a teen can be really hard and there are some that are not sure of how to deal with these feelings so they try to find ways to suppress them; they find their escape in drugs. Often, teens self worth depends on the approval of peers which is one of the reasons they might start using—even if they know their actions/behaviors are destructive. Then there are the few that find healthy coping mechanisms and don’t result to using drugs. The more that a teen is exposed to alcohol, other drug use, and other unhealthy mechanisms, the more likely they are to start using/doing it themselves.
good luck my friend. i hope this helps :)