Peer acceptance and social norms gain a significantly greater hand in directing behavior at the onset of adolescence; as such, the alcohol and illegal drug habits of teens tend to be shaped largely by the substance use of friends and other classmates. In fact, studies suggest that more significantly than actual drug norms, an individual's perception of the illicit drug use by friends and peers is highly associated with his or her own habits in substance use during both middle and high school, a relationship that increases in strength over time. Whereas social influences on alcohol use and marijuana use tend to work directly in the short term, peer and friend norms on smoking cigarettes in middle school have a profound effect on one's own likelihood to smoke cigarettes well into high school. Perhaps the strong correlation between peer influence in middle school and cigarette smoking in high school may be explained by the addictive nature of cigarettes, which could lead many students to continue their smoking habits from middle school into late adolescence.

What does the alcohol and illegal drug habits of teens tend to be shaped by?