Young people's choices about using drugs and alcohol are influenced by peers—not only close friends, but also sports teammates. A new study of middle schoolers and their social networks has found that teammates' smoking plays a big role in youths' decisions about smoking, but adolescents who take part in a lot of sports smoke less.

The study was conducted at the University of Southern California (USC) and appears in the journal Child Development.

Researchers looked at 1,260 ethnically diverse, urban, middle-class sixth through eighth graders. They asked the students about their own smoking behavior, and they asked them to name friends at school as well as the organized they took part in at school. Then, using a social network method they developed, they examined how participation in sports with teammates who smoked affected adolescents' smoking behavior.

They found that youths were more likely to smoke as they were increasingly exposed to teammates who smoked, and that this tendency may be stronger among girls than boys. But they also found that youths who took part in a greater number of sports were less likely to smoke than those who participated in fewer.

"This result suggests that on athletic teams influence the smoking behavior of others even though there might be a protective effect overall of increased participation in athletics on smoking," according to Kayo Fujimoto, assistant professor of health promotion and behavioral sciences at the University of Texas Health Science Center at Houston, who led the study when she was at USC.

The study has implications for programs aimed at preventing teens from . "Current guidelines recommend the use of peer leaders selected within the class to implement such programs," Fujimoto points out. "The findings of this study suggest that peer-led interactive programs should be expanded to include sports teams as well."