During the teen years children often try to gain independence from their parents. They can push limits, break rules and overstep boundaries. Many of them are not satisfied with their appearance, their families and other things about them. So they often suffer from low self-esteem. As a result teenagers often collide with depression. In order not to feel lonely they tend to join some groups. Usually these groups consist of unformal youth.
Young people think adult life as a life full of freedom, independence and let themselves try "adult things" like drinking or staying out at night.