Both peer behavior and adolescents' perceptions of peer behavior predicts risky activities, such as smoking, alcohol use, and marijuana use.

Studies have shown that both actual peer behavior and adolescents' perceptions of peer behavior can significantly predict risky behaviors like smoking, alcohol use, and marijuana use. When a teenager believes that their peers engage in these behaviors frequently, they are more likely to participate in them themselves. Additionally, if a teenager's peers are actually engaging in these behaviors, there may be social pressure to do the same.