Substantial evidence shows that peers are the single biggest social factor in predicting adolescent health behavior. Indeed, the positions of young people in their social networks and the norms and values of their friends and romantic partners are strong predictors of whether they engage in healthy or unhealthy behaviors (Bearman & Bruckner 2001, Gaughan 2006). Parents maintain substantial influence over young people, but the health significance of parent-child relations is intricately tied up with the peer world once children become more independent (e.g., going to school, driving) (see review by Steinberg & Morris 2000). Parent and peer influences both contradict and reinforce each other, although peers tend to have stronger influence on more immediate behavioral decisions (e.g., whether to drink at a party) (Knoester et al. 2006, Marshal & Chassin 2000, Steinberg & Morris 2000). The relative strength of different social influences varies, but the constellation of social ties, not any single social tie, matters most for health habits in adolescence and sets the stage for social ties and health habits in adulthood.
