The Power of Peer Influence: New Findings on When Student Leaders Change Behavior and When They Don’t

Veenstra, R. (2026). Harnessing peer influence: A summary and synthesis of social network and peer-led intervention research. International Journal of Behavioral Development, 50(2), 272–283. https://doi.org/10.1177/01650254251331201

Introduction

Adolescent well-being has declined, and adult-led programs lose traction as teenagers turn away from teachers. Anti-bullying programs, for example, work less well in secondary school than in primary school (Veenstra, 2026). In a new review, René Veenstra of the University of Groningen asks when training peer leaders actually changes behavior. He tests a core assumption behind these programs: that behavior spreads through friendship networks.

Methods

Veenstra brings together two bodies of research across five areas: bullying, internalizing problems, substance use, healthy lifestyles, and sexual behavior. The first is longitudinal social network studies, most of which use statistical models that separate selection (choosing friends who are already similar) from influence (becoming more alike over time). The second is randomized trials of school-wide peer-led programs, which usually pick student leaders through peer nominations. The review is a narrative synthesis based on a keynote address, not a systematic review.

Results

Peer-led programs work when they target behaviors that actually spread from peer to peer. Smoking shows why. Peer influence on smoking is strongest before age 15. After that, similarity among friends mostly reflects selection. ASSIST trained 12- to 15-year-olds to talk informally with friends and cut the odds of smoking by 22%. Towards No Drug Abuse, aimed at 16- and 17-year-olds, did not work. ROOTS reduced school conflict, and popular students did the most to shift norms. Sources of Strength improved norms around seeking help and strengthened students’ ties to adults. Four recent physical activity and obesity programs showed no effect.

Discussion

Veenstra argues that success depends on timing, choosing positive leaders, reaching a critical mass of about 15% of students, and keeping the message simple. The AHEAD program’s dual focus on diet and exercise proved too complicated for students to pass along informally. Peer programs are also expensive, and the strongest ones pair peer leaders with adults.

Implications for mentoring programs

Peer and adult mentoring work best together. In one vaping-prevention program, students connected to both peer leaders and adults were less likely to vape. Programs should choose peer mentors for warmth and standing within the group, not popularity alone, because leaders who seek personal gain can harm a classroom. Goals should stay narrow, and programs should work with young people’s desire for status and respect rather than against it.

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