However, in heavy chronic users, traces can sometimes be detected for weeks after they have stopped using marijuana. Contrary to popular belief most teenagers have not used marijuana and never will. Fewer than one in four high school seniors is a current marijuana user. There are many reasons why some children and young teens start smoking marijuana. Most young people smoke marijuana because their friends or brothers and sisters use marijuana and pressure them to try it.
Some young people use it because they see older people in the family using it.
Others may think it's cool to use marijuana because they hear songs about it and see it on TV and in movies. Some teens may feel they need marijuana and other drugs to help them escape from problems at home, at school, or with friends.