The study found that such a programme reduce their drug use by approximately 15 percent compared to traditional programmes.
"Most substance abuse prevention programs disseminate information about the bad effects of drugs and teach resistance skills without considering the impact of peer influence," said Thomas Valente, Ph.D., assistant professor of preventive medicine at the Keck School of Medicine of USC.
"Generally, our study emphasizes the power of peers. We found that social network-tailored prevention curricula can be very successful in achieving long-term behavioural changes in teenagers," he added.
The study compared substance use among students participating in the prevention program Project Towards No Drug Abuse (TND), traditionally led by a health educator or teacher, to the modified peer-led Project TND Network. TND held interactive discussions at the classroom level while TND Network divided the students into smaller groups composed of their friends, increased the number of group activities and a student-chosen leader led the discussion.
"Reducing drug use among the high-risk teen population at these alternative schools is tough," continues Valente.
"It is encouraging to see this type of positive influence among students who live and go to school in challenging environments,' Valente added.
However, the study also found that students with a peer environment friendly for substance use did not benefit from the interactive program.
"Peer influence can go both ways, some students benefited because of the positive social influence of their friends while others were harmed by negative influence of their substance using peers," concludes Valente.
"Programs that incorporate this type of interactive programming can be very effective, but they depend on how peer influence is channelled," he added.
The study will appear in the journal Addiction.