Harnessing peer influence: A summary and synthesis of social network and peer-led intervention research

Abstract

This article synthesizes recent research on social network dynamics and peer-led interventions to address adolescent behaviors in five domains: bullying, internalizing problems, substance use, healthy lifestyles, and sexual behaviors. Social network studies highlight the role of peers in shaping norms, behaviors, and group dynamics. Peer-led interventions take advantage of these dynamics by training influential peers to promote positive behaviors and counteract maladaptive norms. Interventions such as ROOTS, ASSIST, and Sources of Strength demonstrate the potential of peer-led strategies to reduce bullying, substance use, and suicidal ideation. However, the effectiveness of such interventions varies and is often limited by inconsistent leadership, implementation challenges, and the age-dependent nature of peer influence. Successful interventions require strategic selection of leaders, establishment of critical mass and positive social norms, and integration with adult mentorship or systemic support. This synthesis highlights the need for cost-effective models that leverage peer influence to improve adolescent health and well-being, while addressing the challenges of scalability and sustainability.

Keywords

Peer influence intervention program social norms bullying depression substance use smoking physical activity sexual behaviors adolescence

Introduction

Adolescent mental well-being has declined significantly in recent years (Allen, 2024). These challenges are often exacerbated by poor peer relationships during adolescence, which predict long-term negative outcomes, including future mental health problems, poor academic performance, and even early mortality (Holt-Lunstad et al., 2010; Loeb et al., 2019). To address these pressing concerns and mitigate their lasting impact on the lives of adolescents, interventions that promote positive behaviors and change social norms are essential.

Traditional teacher-led interventions have demonstrated limited success in addressing negative behaviors such as substance use during adolescence (Henneberger et al., 2019) and may even be counterproductive in tackling bullying by mid-adolescence (Yeager et al., 2015). Adolescents may resist adult-led strategies, especially as they seek autonomy and begin to view teachers as less trustworthy sources of guidance. This limits the potential of teacher-led approaches to create meaningful, lasting change.

Peer-led interventions leverage adolescents’ peer relationships to promote positive behaviors and change social norms, providing a more effective alternative for addressing behavioral challenges (Veenstra & Laninga-Wijnen, 2022). Adolescents are more likely to internalize information from peers because they perceive peer communication as less intimidating and more relatable. These interventions use a key mechanism known as diffusion of behavior, in which trained peer leaders foster relationships within their school and influence their peers through both formal and informal interactions. This influence often extends beyond structured sessions into everyday conversations and social activities, creating lasting behavior change. Peer-led interventions are also in line with participatory research approaches, in which the people who are actually affected are heavily involved.

This article examines universal peer-led interventions in five areas: bullying, internalizing problems, substance use, healthy lifestyles, and sexuality. All reviewed studies use randomized controlled trials and select adolescent leaders from their classmates or grademates. Some programs rely on school staff to identify students whose “voices are heard” (Wyman et al., 2010), but most ask students to nominate good leaders (Campbell et al., 2008; Mitchell et al., 2021; Valente et al., 2007). This helps to identify those who naturally possess leadership qualities. Some focus on socially influential students (Golonka et al., 2017), while others identify collaborative leaders by asking who peers would choose for group work (Valente et al., 2007).

The mechanisms behind peer-led education remain unclear (Dobson et al., 2017). This article examines the key assumption of behavior diffusion, integrating social network research. Social network analysis helps distinguish between selection (“birds of a feather flock together”) and influence (“one bad apple spoils the whole barrel”). Most studies reviewed are longitudinal social network studies using stochastic actor-oriented models (Snijders et al., 2010).

Systematic reviews exist for peer-led interventions on internalizing problems (King & Fazel, 2021), substance use (Clarke et al., 1986; Cuijpers, 2002; MacArthur et al., 2015), and healthy lifestyles (Christensen et al., 2021), along with a global review covering substance use, healthy behaviors, and HIV prevention (Dodd et al., 2022). This article emphasizes the refinement of peer-led strategies to harness peer influence.

The Role of Similarity in Friendship and Group Dynamics

This section examines how behavioral similarities form among friends and their implications for peer-led interventions. Similarity stabilizes relationships through two key mechanisms (Laursen & Veenstra, 2021). First, it strengthens compatibility. Friends influence each other to minimize differences and increase similarities. As adolescents mature, they recognize that successful relationships require concessions, such as conformity and self-restraint (Shulman & Laursen, 2002). Similarity fosters joint activities, positive experiences, and deeper interdependence. It also facilitates communication, enhances belonging, and reinforces social identity, making relationships more rewarding and stable by reducing misunderstandings and fostering trust.

Second, similarity reduces conflict. Fewer differences mean fewer disagreements, which protects friendships. Friends are less likely to engage in uncompromising conflicts than non-friends or family members (Laursen & Veenstra, 2021). Friendships are more likely to dissolve when individuals differ in school performance, aggression, anxiety, or depression (Guimond et al., 2019; Hartl et al., 2015).

Friend similarity arises through influence, as individuals adopt behaviors and attitudes of their peers, aligning with social cognitive learning theory (Bandura, 1977). Social rewards (e.g., status) and punishments (e.g., rejection) further shape behaviors. However, social network research highlights the need to distinguish influence from selection—if similarity stems from selection, peer-led interventions based on behavior diffusion may be ineffective.

In group contexts, similarity enhances cohesion, reinforces norms, and streamlines collaboration (Veenstra & Lodder, 2022). It reduces exclusion risks and fosters belonging. When group norms align with intervention goals, positive peer influence is enhanced; when group norms conflict with intervention goals, negative effects can occur. Thus, the success of peer-led interventions depends on group norms.

Bullying

Social network studies of bullying suggest that bullies befriend other bullies to collectively target victims and that the friends of bullies may initially assist them before being influenced to direct bullying toward victims (Huitsing et al., 2014; Rambaran et al., 2020; Sentse et al., 2014). Among students under the age of 12, friendships do not appear to be formed based on similarities in victimization, and friends do not appear to significantly influence each other’s levels of victimization (Berger et al., 2019; Rambaran et al., 2020). In contrast, among students aged 12 and older, friends are often selected based on general victimization (Lodder et al., 2016), as well as physical (Sentse et al., 2013) and relational victimization (Sijtsema et al., 2013), and friends influence each other’s levels of victimization.

Bullies can foster a culture of fear (Van der Ploeg et al., 2020). High-status bullies tend to increase their power by seeking out new victims rather than targeting the same victims over time, unlike low-status bullies. Other research suggests that students’ relative social status is often established at the beginning of secondary school. Those who assert dominance in the first few weeks of school tend to gain and maintain popularity without facing social consequences. However, students who persist in bullying maintain their status but also experience increasing levels of peer rejection (De Vries et al., 2021). These findings underscore that bullying is a complex group phenomenon driven by the pursuit of social standing and that a network perspective deepens our understanding of the connection between bullying and peer status.

Social norms are important for understanding bullying processes (Veenstra & Lodder, 2022). If the association between bullying and popularity in a classroom is positive, indicating a pro-bullying norm, most students will conform to this norm to gain external benefits such as social approval and inclusion. Conversely, nonconformity can lead to a misfit effect, resulting in negative outcomes such as social sanctioning, exclusion, and rejection (Bass et al., 2022). When students perceive that bullying is associated with social status, they are less likely to defend victims out of concern for their position within the peer group (Peets et al., 2015).

At the same time, pluralistic ignorance (Miller & McFarland, 1991) also plays a role in bullying. Most students privately disapprove of bullying, but mistakenly believe that most of their peers accept it. Out of a desire for social approval, inclusion, and status, they suppress dissent and imitate and reinforce the bullying of popular classmates. This reinforcement of the false belief that bullying is widely accepted ultimately diminishes efforts to defend victims (Veenstra & Lodder, 2022).

In classrooms where both negative (i.e., aggression) and positive (i.e., prosociality) behaviors were associated with popularity, the aggressive norm dominated (Laninga-Wijnen et al., 2020). This suggests that aggression may overshadow prosocial behavior when both are linked to popularity. Aggression is often more visible and impactful, attracting attention through fear or admiration and making it easier to imitate. As a result, students are more likely to follow the aggressive norm rather than the prosocial one.

Another network study examined the impact of perceived norms rather than social norms and found that adolescents who viewed bullying favorably were more likely to use it as a basis for selecting friends (Shin, 2022). This dynamic led bullies to associate primarily with peers who also engaged in high levels of bullying. Furthermore, elevated perceived bullying norms strengthened peer influence on both bullying and victimization. Bullies who expected positive outcomes were more likely to adopt the aggressive behaviors of their most bullying friends. When students perceived bullying as socially acceptable, they were less likely to empathize with or intervene on behalf of victims for fear of becoming targets themselves. Consequently, perceptions of pro-bullying norms exacerbated victimization experiences and intensified friendship influence on victimization (Shin, 2022).

Peer-Led Intervention to Reduce Bullying

Aligned with social network research showing that classroom norms influence bullying and that bullying often boosts popularity, the ROOTS peer-led intervention encouraged students to identify common conflicts and take a stand against bullying through activities such as creating posters, writing slogans, and handing out wristbands as rewards. The intervention consisted of 10 biweekly sessions, each lasting 45 to 60 min (Paluck et al., 2016). The intervention was implemented in Grades 5 through 8 in U.S. public middle schools. Students invited to the intervention sessions were randomly selected to represent 15% of the school population by grade and gender. Compared to control schools, intervention schools showed a 25% reduction in peer conflict, as evidenced by fewer disciplinary reports. Students in intervention schools also reported more discussions about conflict reduction with friends. Consistent with social network research (Dijkstra et al., 2008; Laninga-Wijnen et al., 2017), popular students (i.e., social referents) were most successful in setting the norm and spreading perceptions of conflict as less socially normative.

The ROOTS intervention was also implemented in 12 Indonesian secondary schools. In ROOTS-Indonesia, students nominated peers with whom they spent the most time, and those with the most nominations were selected as peer leaders (Bowes et al., 2019). These students participated in weekly meetings with a trained facilitator to identify conflict behaviors and take a public stance against them. They developed anti-bullying activities, such as creating posters or rewarding positive behaviors, and were encouraged to involve parents and teachers. A feasibility study showed that ROOTS-Indonesia reduced negative social norms and that it is a promising strategy for tackling bullying (Zaneva et al., 2023).

Internalizing Problem Behaviors

Adolescents who have difficulty forming peer relationships are at risk for negative outcomes. Adolescents who are excluded by their peers may develop feelings of inferiority and internalizing problems, such as depressive symptoms and social anxiety. These internalizing problems also interfere with adolescents’ ability to form meaningful relationships with peers (Schaefer et al., 2011). Influence and selection processes contribute to depressive symptoms and social anxiety. Adolescents tend to select friends who are similar in these internalizing problems (Neal & Veenstra, 2021). This can be risky because depressed adolescents can reinforce each other’s depression levels through co-rumination, where they repeatedly talk about problems, speculate and reinforce negative feelings (Rose, 2002). Peers can also influence each other’s level of social anxiety, with girls being more affected than boys in early adolescence (Van Zalk & Van Zalk, 2015). This mutual reinforcement of negative emotions can deepen their challenges and hinder emotional recovery. Depressed adolescents may find it more beneficial to have more non-depressed peers as friends. However, friendships between depressed and non-depressed friends often fall apart. Adolescents with depressive symptoms have difficulty maintaining close relationships due to a lack of social skills. This difficulty can lead to dissatisfaction among their non-depressed friends, often resulting in the termination of these relationships (Kiuru et al., 2012; Van Zalk et al., 2010). A similar dynamic is observed with happiness. Students whose friends are less happy than they are tend to be influenced by their friends’ negative moods, which can lead to an increase in their own negative feelings. These mood changes may cause individuals to reevaluate the friendship, making it more likely to end (Van Workum et al., 2013). These negative experiences can create a vicious cycle in which depressed adolescents become even less happy because of their depressed friends or by breaking friendships with non-depressed friends. In addition, a persistent negative mind-set often creates a fertile ground for other harmful behaviors. Research has shown that students with many depressed friends are more likely to engage in self-harming behaviors than those without such friends (Giletta et al., 2013).

Social network studies have examined the role of online friendships in compensating for a lack of offline social connections. Virtual interactions can provide a safe space for shy adolescents to form meaningful relationships (Van Zalk et al., 2014). These online connections were shown to increase self-esteem and eventually lead to the development of more offline friendships, highlighting the potential of digital networks for peer-led interventions to support social development and mental health.

Research conducted in China found little evidence for selection and influence processes related to depressive symptoms (Fu et al., 2021; Qin et al., 2023). Another study found that friendship selection was influenced by similarity in depressive symptoms, although this effect decreased with pubertal maturation, probably because early-maturing adolescents tend to experience higher levels of depression than their normal or late-maturing peers (Yu et al., 2023).

Peer-Led Intervention to Prevent Suicidal Ideation

There are no peer-led interventions for depressive symptoms or social anxiety. However, the Sources of Strength peer-led intervention was designed to prevent suicidal ideation among 16-year-olds. This intervention recruited peer leaders—ranging from 1.3% of the student population in the largest intervention school to 14.4% in the smallest intervention school—to participate in 4 hr of interactive training (Wyman et al., 2010). The training, delivered by certified trainers, emphasized strengthening sources of strength, including family, friends, adult mentors and services, and engaging trusted adults to support distressed and suicidal peers. Peer leaders showed improved adaptive norms around suicide, stronger connections to adults, and increased school engagement, with the most significant gains seen in those who started with less adaptive norms. Among their peers, the intervention increased perceptions of adult support for suicidal youth and the acceptability of seeking help, with the greatest improvement among students with a history of suicidal ideation. Being female, being close to a peer leader, having more friends and trusted adults increased exposure to the intervention, while suicide attempts decreased exposure (Pickering et al., 2018).

Social network research shows that adolescents with internalizing behaviors often select friends with similar issues, reinforcing negativity through co-rumination. In addition, non-depressed peers may distance themselves due to dissatisfaction with the friendship. However, the Sources of Strength intervention improved perceptions of adult support for suicidal youth and increased the acceptability of seeking help. By fostering stronger connections with trusted adults, the intervention helps compensate for the lack of supportive peer relationships (Wyman et al., 2019).

Substance Use

Peers play a significant role in students’ tobacco use (Henneberger et al., 2021). Peer influence is more pronounced among students younger than 15 years. Younger students often encourage and reinforce smoking behavior within their peer groups (Mercken et al., 2009; Steglich et al., 2010). Another study also found evidence of peer influence on smoking behavior in early adolescence in China, but did not observe effects of friendship selection based on smoking (DeLay et al., 2023). Similar selection and influence processes have been observed in adolescent e-cigarette use. Adolescents may start vaping as a way to gain acceptance or to strengthen their position in the social hierarchy (Valente et al., 2023). As with other risky behaviors, peer influence plays a significant role in the initiation and continuation of e-cigarette use. In contrast, among students aged 15 and older, smoking behavior is primarily shaped by selection. These students are more likely to associate with peers who already smoke, a tendency related to the diminished influence of the environment once smoking becomes an addiction (DeLay et al., 2013; Mathys et al., 2013). The social dynamics of smoking are further reinforced by designated smoking areas, where smokers naturally form connections with each other. After the age of 15, smokers generally have little or no influence on encouraging their peers to start smoking. To reduce the prevalence of smoking and vaping, especially in peer groups, interventions targeting adolescents before the age of 15 are critical. Early peer-led interventions can help curb the initiation of smoking and vaping and reduce its spread within peer groups.

Peers have a significant influence on the initiation of alcohol use among adolescents (Henneberger et al., 2021). Students with many friends who drink are more likely to be exposed to social contexts where drinking occurs, such as parties. These students also receive more social approval for drinking, which can encourage them to start drinking (Osgood et al., 2013). Influences on alcohol use extend beyond close friendships and also occur within indirect relationships. Adolescents can be affected by their friends’ friends, especially in social settings where they encounter these indirect connections. The norms of such settings—for example, the acceptance of drinking—and the desire to belong can drive alcohol use even among those with only indirect connections (Cheadle et al., 2013). Another study identified peer influence on alcohol use among Chinese adolescents but found no evidence of friendship selection based on drinking behaviors (DeLay et al., 2023).

Peers also play a role in cannabis use (Torrejón-Guirado et al., 2023). A key factor is whether friends have experimented with cannabis. Adolescents who have tried cannabis are more likely to form friendships with others who have also used it, creating a reinforcing network of influence. Conversely, students who have never experimented with cannabis are more likely to form friendships with others who share the same behavior. However, within mixed groups, non-users can still be influenced by peers who have used cannabis, highlighting the role of peer dynamics in shaping substance use behavior (de la Haye, Green, et al., 2013).

Peer-Led Interventions to Prevent Harmful Substance Use

Social network research on substance use has shown that peer influence on smoking is greatest before the age of 15. This explains why ASSIST (A Stop Smoking In Schools Trial), which targeted smoking prevention in early adolescence, was effective. The ASSIST smoking prevention program targeted 12- to 15-year-olds by training 835 peer leaders—15% of all students—to act as peer supporters during informal interactions outside the classroom over a 10-week period (Campbell et al., 2008; Starkey et al., 2009). Peer leaders underwent a 2-day training that focused on the short-term risks of smoking for young people and the health, environmental, and economic benefits of being smoke-free. The training emphasized communication skills, teamwork, expression of feelings, cooperation, conflict resolution, and personal development. The intervention leveraged informal channels of peer influence by encouraging peer supporters to engage with individuals they identified as receptive to antismoking messages. These peer-led efforts reduced the odds of smoking by 22% in intervention schools compared with control schools (Campbell et al., 2008).

Social network research on substance use has shown that smoking similarity is due to selection after the age of 15. This explains why the Towards No Drug Abuse peer-led intervention, which targeted tobacco, alcohol, and drug use prevention in late adolescence, was not effective. Towards No Drug Abuse aimed to prevent substance abuse among 16- to 17-year-olds, recruited peer leaders—who comprised 19% of the student population—to deliver 12 intervention sessions over 3–4 weeks (Valente et al., 2007). These peer leaders received a 1-hr training focused on leadership skills, normative restructuring regarding substance use, facilitating group discussions, and managing group interactions. The intervention specifically targeted harmful substance use behaviors related to tobacco, alcohol, cannabis, and cocaine.

Consistent with advances in social network research, the study underscores that peer influence is shaped by friendship and group dynamics. Peer interactions can amplify both positive and negative influences. For example, students with few substance-using peers benefited from the intervention because positive social influences were reinforced by their peers. Conversely, students surrounded by substance-using peers were more likely to experience negative influences. These findings underscore the central role of peer influence in both beneficial and adverse outcomes (Valente et al., 2007).

Another Toward No Drug Abuse study examined gender differences in peer influence on substance use (Kwan et al., 2015). Male adolescents were influenced by social norms surrounding risky behaviors and drug use, often aligning themselves with these behaviors to increase their status. Conversely, females were less likely to use misconduct to gain acceptance. Instead, the peer-led intervention promoted positive engagement among females, leading to reduced substance use.

More recently, two vaping interventions have been proposed: a trial in Pittsburgh (Chu et al., 2021) and Above the Influence of Vaping (Wyman et al., 2021). In the Above the Influence of Vaping intervention, staff identify 10%–15% of students (13–14 years old) as peer leaders and assign and train (4–6 hr) one adult advisor for every eight peer leaders. Peer leaders and adult advisors then attend a 4-hr workshop on vaping risks, accurate facts, and supportive relationships. During dissemination, peer leaders implement four campaigns using message and activity templates (e.g., classroom presentations, videos) to build resilience and reinforce anti-vaping norms. Findings suggest that engaging adults and strengthening youth-adult connections may be critical to effective peer-led interventions (Wyman et al., 2021). Students with connections to not only peer leaders but also adults were less likely to report vaping or intentions to vape. In line with social network research, this intervention focused on early adolescents, which is critical to preventing initiation and limiting the spread of e-cigarette use within peer groups.

Healthy Lifestyles

Peer influence plays a significant role in shaping adolescents’ health-related lifestyles. A social network study identified three distinct lifestyle patterns among adolescents: a mostly healthy lifestyle, a discordant lifestyle, and a mostly unhealthy lifestyle (Adams et al., 2022). The healthy group consisted of individuals who refrained from smoking, drinking, and engaging in risky sexual behaviors, and who regularly wore seatbelts. The unhealthy group exhibited high levels of substance use, risky sexual behavior (e.g., not using condoms), and low levels of physical activity. The discordant group showed mixed patterns that varied between schools. Adolescents tended to select friends based on these lifestyle patterns and, in turn, influenced each other’s lifestyle choices. These findings suggest that adolescents are likely to adopt an entire lifestyle bundle.

Other social network research has examined individual health-related behaviors. Adolescents tend to befriend peers with similar physical activity levels and often emulate their friends’ behaviors (de la Haye et al., 2011; Long et al., 2017; Simpkins et al., 2013). Friendships also form between individuals with similar body mass index (BMIs) or weight control practices, with friends influencing each other’s weight and subsequently were affected by their friends’ weight (Shoham et al., 2012; Simpkins et al., 2013), but not their weight control behavior (Simone et al., 2018). Another study on weight status changes and weight-related lifestyles found that adolescents tended to select friends with similar weight status and weight-related lifestyles (Lee et al., 2022). However, the study found no evidence of peer influence on adolescent weight change. In addition, adolescents’ junk food consumption was influenced by the consumption of their school friends (de la Haye, Robins, et al., 2013). Over the course of a school year, students’ intake mirrored that of their best friends in the same grade. Those with low-consumption friends adopted or maintained lower intakes, while those with high-consumption friends mirrored higher levels of consumption.

Peer-Led Interventions to Prevent Obesity and Increase Physical Activity

While an older study suggested that peer leaders could be effective in a nutrition intervention (Birnbaum et al., 2002), and although social network research suggests that adolescents can influence their healthy lifestyles, several recent peer-led interventions show no evidence of impact. AHEAD (Activity and Healthy Eating in ADolescence) is a peer-led obesity prevention program for 12- to 13-year-olds (Bell et al., 2017). Peer leaders attended a 2-day training to build knowledge, skills, and confidence to informally promote healthy eating and physical activity to their peers while modeling small, manageable changes in their own behavior. They used diaries to track interactions and were given “healthy challenges” to encourage personal behavior change. While the intervention was feasible and well received, it was resource-intensive and costly, with no evidence of impact on adolescents’ physical activity or healthy eating. The dual focus on diet and activity proved too complex for informal peer influence, highlighting the challenge of balancing comprehensive health promotion with the need for clear, focused messages (see for a social network-based intervention that uses peer influence to promote water consumption: Smit et al., 2016).

In PLAN-A, a peer-led physical activity intervention for 13- to 14-year-old girls, the top 18% of girls nominated by their peers in intervention schools received 3 days of training to promote and support physical activity (Jago et al., 2021). Participants wore accelerometers for 7 days to measure the primary outcome: average weekday minutes of moderate-to-vigorous physical activity. The intervention did not increase physical activity levels or demonstrate cost-effectiveness.

A peer-led intervention promoted physical activity among 12-year-old students by training the top 15% most influential adolescents (based on peer nominations) to encourage activity among their classmates (Van Woudenberg et al., 2018). Participants used smartphones for surveys and wore accelerometers to track steps. There was no significant intervention effect on physical activity. A related study compared the effectiveness of a social network intervention, a mass media intervention, and a control condition in promoting physical activity among 11-year-old students (Van Woudenberg et al., 2020). In the social network intervention, 15% of participants (based on peer nominations) became influencers and created physical activity vlogs that were displayed during the intervention. In the mass media condition, participants viewed the same vlogs from the social network intervention without knowing these peers. The control group did not receive any physical activity vlogs. All participants used a research smartphone for surveys and wore a wrist accelerometer to track activity. The study found no evidence that the interventions were effective in increasing physical activity among adolescents, which is consistent with the other peer-led healthy lifestyle interventions.

Sexuality and Sexual Behaviors

Adolescent romance is embedded in interconnected social communities in which dating is more likely if romantic partners were friends, had mutual friends, or were connected through friends who are part of a couple (McMillan et al., 2025). Adolescents with friends who have had sex are more likely to experience sexual debut (Trinh et al., 2019). Friendship selection based on sexual debut is stronger for girls, likely due to greater social scrutiny and sanctions regarding their sexual attitudes and behaviors. While both boys and girls gain perceived popularity with more sexual partners (Kreager et al., 2025; Trinh et al., 2019), gender disparities persist. Girls with more sexual partners tend to lose friendships and face increased peer dislike, whereas boys who report similar behaviors do not face these social penalties (Kreager et al., 2025).

Social relationships between ingroup and outgroup members have been theorized to reduce prejudice (Allport, 1954). A social network study examined whether friendships between adolescents of different sexualities influence homophobic attitudes (McMillan et al., 2023). Results suggest that heterosexual adolescents with sexual minority friends exhibit less homophobia, with gender playing a larger role (6.4% of heterosexual girls’ friendships involve sexual minority peers, compared to 3.5% for heterosexual boys) than the friendships themselves. Another study found that among elementary school children, the social acceptance of gender-referred children varied according to the sex of their classmates (Wallien et al., 2010). Gender-referred boys were more accepted by female classmates and rejected by male classmates, while the opposite was true for gender-referred girls. Relationships with cross-gender classmates were generally more positive than those with same-gender classmates. Gender-referred children were no more likely to be bullied than other children.

Peer-Led Intervention to Promote Sexual Health

Social network research shows that peer networks shape sexual debut and relationship norms, with gender differences influencing social sanctions. A study found that students engaged more openly in peer-led sex education, asking questions, debating, and using humor, while teacher-led sessions felt authoritarian (Dobson et al., 2017). Peer-led education fosters open dialogue and helps adolescents navigate sexual discussions beyond the classroom. Both girls and boys preferred peer-led sessions, although 57% of girls and 32% of boys preferred same-gender discussion groups (Stephenson et al., 2004).

STASH (Sexually Transmitted infections And Sexual Health) is a peer-led intervention designed to promote sexual health among 14- to 16-year-olds. The intervention trained peer-nominated students to share sexual health information through face-to-face interactions and private Facebook groups (Broccatelli et al., 2021). After completing 2 days of training, peer leaders used their Facebook accounts to create private groups, invite friends to join, and share carefully selected educational content from the STASH website, including memes, infographics, and quizzes. These private groups provided a safe and comfortable space to discuss sensitive topics, with ongoing support from STASH trainers over a 5- to 10-week period. In 2017, Facebook was the only platform that met the intervention’s requirements for privacy and functionality, as opposed to more popular platforms at the time, such as Snapchat, WhatsApp, and Instagram (Purcell et al., 2023). Consistent with social network research, students with similar sexual health behaviors, such as knowledge or openness to discussing sexual health, were more likely to form friendships (Broccatelli et al., 2021). The intended outcomes of STASH included improved well-being among peer leaders, healthier intimate relationships, delayed initiation of sex or abstinence, increased condom use, and “competent” sexual behavior (Mitchell et al., 2021). To date, the impact of the intervention on these outcomes is unknown.

Discussion

This article synthesizes recent empirical research on social network dynamics and peer-led interventions, with a focus on bullying, internalizing problem behaviors, substance use, healthy lifestyles, and sexuality and sexual behaviors. Table 1 summarizes key findings. Social network research highlights the powerful role of peers in shaping adolescent behaviors and norms. Adolescents often form friendships with those who share similar behaviors and attitudes, which can magnify both positive and negative influences within the group. Interventions can capitalize on these dynamics by strategically engaging influential peers to promote positive behavior change in their networks.

Table 1.

Key Findings from Social Network and Peer-Led Intervention Research on Peer Influence.

Topic	Social Network Research	Peer-Led Interventions
Bullying	• Bullying affects social status and high-status bullies often target new victims. • Classroom norms shape bullying behavior and acceptance.	• The ROOTS intervention helped reduce conflict by motivating students to oppose it through activities such as creating posters and using peer leaders to change social norms.
Internalizing Problem Behaviors	• Depressed adolescents often reinforce each other’s negative emotions. • Non-depressed peers often avoid friendships with depressed peers.	• Sources of Strength improved suicide prevention norms and connections to adults. • Peer leaders positively influenced help-seeking behavior.
Substance Use	• Smoking and vaping are strongly influenced by peers, especially before the age of 15. • Peer similarity is due to selection after age 15.	• ASSIST reduced smoking initiation through informal peer influence. • New vaping interventions emphasized early prevention.
Healthy Lifestyles	• Adolescents adopt broader health-related lifestyles or individual health behaviors from their peers.	• Recent peer-led interventions were not effective in changing physical activity or dietary behaviors.
Sexuality and Sexual Behaviors	• Peer networks shape sexual debut and relationship norms. • Gender differences affect social sanctions for sexual behaviors.	• STASH facilitated sexual health discussions through online peer interactions. • Finding suitable online platforms for a peer-led intervention is challenging.

Peer-led interventions present a promising alternative to traditional teacher-led approaches, which often lose effectiveness during adolescence (Cuijpers, 2002; Tobler et al., 2000). By utilizing the natural influence of peers, these interventions aim to mitigate negative behaviors while promoting positive ones. Their success relies on diffusion of behavior, as trained peer leaders engage peers through both structured and informal interactions, making the interventions relatable and impactful.

Peer-led interventions often identify leaders through student nominations to ensure they possess characteristics such as popularity, collaborative skills, or accessibility. Studies recommend selecting at least 15% of the group as leaders to achieve a “critical mass” of influence and increase the reach and visibility of the intervention (Bell et al., 2017; Pickering et al., 2018). This synthesis highlights the potential of peer-led approaches to harness social networks for lasting, positive behavior change and offers several valuable lessons:

Peer-led interventions have potential in adolescence to increase information retention, establish lasting norms, and promote peer integration, particularly as the effectiveness of adult-led methods declines: Key benefits of peer-led interventions include improved retention of information, creation of lasting social norms, and smoother integration within peer groups compared to teacher-led interventions. For instance, adult-led anti-bullying interventions are effective in primary school, when parents and teachers are involved in children’s social lives, but tend to struggle in secondary school, when peers disengage from adult culture (Yeager et al., 2015). Adolescents feel increasingly closer to their peers than to their parents as they grow older (Veenstra & Laninga-Wijnen, 2023). This highlights the importance of leveraging peer influence in peer-led interventions during this developmental stage. However, challenges such as inconsistent leadership quality and the potential for unintended messaging remain significant barriers. Interventions such as Sources of Strength and ASSIST illustrate the potential of well-designed peer-led interventions. These initiatives have shown success in promoting adaptive help-seeking behaviors and reducing substance use when supported by comprehensive training and clear goals.

The impact of peer-led interventions depends on timing: An important finding from social network research and peer-led interventions is the age-dependent nature of peer influence on substance use. Younger adolescents are more directly influenced by peers to engage in smoking or vaping (Henneberger et al., 2021; Valente et al., 2023). In contrast, older adolescents show similarity to peers through selection processes and form friendships based on shared behaviors such as smoking or vaping. This developmental shift highlights the need to implement smoking and vaping prevention efforts early, before adolescents develop an addiction.

Effective impact requires the selection and training of positive peer leaders: The selection and proportion of peer leaders involved is critical. Positive leaders, those who build strong relationships and prioritize the group’s well-being, can promote meaningful and lasting behavior change (Dong et al., 2023). Conversely, negative leaders who prioritize personal gain can be detrimental to classroom well-being and undermine intervention goals (Dong et al., 2024). To achieve meaningful impact, most studies recommend designating at least 15% of a group as peer leaders to create a “critical mass” that can effectively influence peer networks (Bell et al., 2017; Campbell et al., 2008; Valente et al., 2007). However, to prevent negative leaders from dominating this critical mass and exerting harmful influence, it is important to transform these negative leaders into positive role models, as demonstrated in a universal anti-bullying prevention program (Dong et al., 2025).

Peer-led interventions can be resource-intensive: While peer-led interventions have great potential, they often require significant resources and can be expensive (Mellanby et al., 2000). Conducting comprehensive cost–benefit analyses is critical to ensuring that these interventions are both scalable and sustainable without sacrificing effectiveness. To reduce costs, such interventions could adopt a model in which trained peer leaders take responsibility for training the next generation of leaders, minimizing the need for adult trainers to return to schools each year. Involving adolescents in the development of interventions can increase their effectiveness and relevance (Christensen et al., 2021).

Middle and high schools could adopt a comprehensive school jobs program (Ellis et al., 2016) in which positive peer leaders in lower grades focus on early prevention efforts, such as addressing smoking, vaping, and bullying, while promoting positive norms among their peers. Meanwhile, peer leaders in upper grades could take on tasks such as connecting distressed or suicidal peers with supportive adults and leading virtual discussions on sensitive sexual health topics to encourage help-seeking behaviors among peers or younger students (Stephenson et al., 2004). In addition, other adolescents may lead a gender and sexuality alliance to improve the school climate for sexual and gender diverse youth (Marx & Kettrey, 2016).

Peer-led interventions often require systemic support that aligns healthy choices with adolescents’ desire for status and respect: The lack of success of peer-led physical activity interventions in achieving sustained behavior change highlights the challenges of translating peer influence into measurable outcomes. These findings suggest that peer-led interventions often require complementary support, such as adult mentorship or institutional support, to maximize their impact. Interventions like Sources of Strength demonstrate the effectiveness of blending peer influence with adult guidance, balancing connection and authority to improve outcomes. Importantly, adults should recognize that behavior change is more achievable by leveraging youth’s existing motivations rather than trying to change their priorities (Yeager et al., 2018). Balancing long-term healthy choices with immediate desires for status and respect may be more effective than trying to get adolescents to prioritize long-term health over short-term social success.

Social norms drive social network dynamics and the effectiveness of peer-led interventions: Changing peer group norms from maladaptive to adaptive has proven critical in domains such as bullying, substance use, and sexual behavior. Interventions like ROOTS that explicitly target social norms have demonstrated sustained reductions in harmful behaviors. Conversely, ignoring these norms can perpetuate maladaptive behaviors, as seen in the normalization of bullying or substance use within certain peer groups.

Digital platforms extend peer influence on sensitive issues beyond physical spaces: Closed Facebook groups provided a safe space for participants in the STASH intervention to discuss sexual health issues, promoting both engagement and accessibility. However, the digital nature of such interventions requires ongoing monitoring of platform popularity, vigilance against misinformation or misuse, and efforts to maintain the intended benefits.

Avenues for Further Research

Peer-led interventions have demonstrated potential, but their effectiveness is age-dependent and varies across behavioral domains. To refine these interventions, future research must delve deeper into the mechanisms of influence within peer networks (Veenstra & Laninga-Wijnen, 2022). Understanding whether peer influence is driven more by direct pressure, imitation, or indirect connections—such as through friends of friends—can clarify how behaviors spread and inform targeted intervention strategies. Key questions include identifying which peers exert the most influence, which youth are most susceptible, and how these dynamics vary by the type and context of the behavior being addressed (DeLay et al., 2022). Another key question is whether peer-led interventions have a long-term effect, such as ASSIST, which was effective in reducing smoking initiation among adolescents for 2 years after its implementation (Campbell et al., 2008).

The processes of friendship formation and dissolution are also critical to understanding behavior change. Research suggests that while peers may encourage initiation of behaviors such as smoking, cessation often occurs independently, driven by external societal norms rather than direct peer influence (Haas & Schaefer, 2014). For example, friends may initially provide access to cigarettes, but cessation tends to occur individually, even when peers continue to smoke. Such findings highlight the importance of considering the bidirectional nature of peer influence when designing interventions.

Social network research in Asia (Mainland China, Korea, Taiwan) and South America (Chile) is often consistent with the more commonly studied American and European samples, suggesting generalizability across cultures. However, data from underrepresented populations are essential for understanding peer influence in diverse social structures and for assessing global intervention effectiveness (Veenstra et al., 2024).

In addition, peer influence extends beyond the domains addressed in this article. There is untapped potential to develop peer-led strategies that target externalizing problem behaviors or academic engagement (Veenstra & Laninga-Wijnen, 2023).

Conclusion

This synthesis highlights the dual role of peer influence in adolescent development, serving as both a risk and an opportunity. When harnessed effectively, the natural dynamics of social networks can be leveraged through peer-led interventions to promote positive behaviors and mitigate risks. However, the success of these interventions depends on several key factors, including strategic design, timely implementation, the establishment of a critical mass of peer leaders, and adaptation to the specific context in which they are applied. These findings underscore the importance of continued innovation and evidence-based refinement to maximize the impact of peer-led interventions and ensure that they are both effective and adaptable to diverse youth populations.

Footnotes

Author’s Note

Presented as a keynote address at the 27th Meeting of the International Society for the Study of Behavioral Development, June 16–20, 2024, Lisbon, Portugal.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

René Veenstra

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