In one of the most ambitious behavioral health experiments yet attempted in the region, researchers have unveiled the protocol for a cluster randomized controlled trial that will test whether an eight-session peer group intervention can simultaneously reduce substance use and reshape inequitable gender beliefs among young people in Zambia, Zimbabwe, and South Africa. The trial, known as PEGISUS — Peer Education for Gender Inclusion and Substance Use in Southern Africa — is embedded directly within existing vocational training programs, a design choice that could fundamentally change how at-risk youth reach and sustain healthier life trajectories. The study protocol, published in Addiction Science & Clinical Practice, describes a two-arm superiority trial recruiting sixty-six peer groups totaling approximately 264 participants aged 16 to 24 across three countries, with the first participants already enrolled since March 2025.
The rationale for targeting both substance use and gender beliefs in a single intervention rests on a growing body of evidence that the two behaviors are deeply intertwined. Across Southern Africa, an estimated 20 to 40 percent of young people report using at least one psychoactive substance, often as a coping strategy against unemployment, fragile health systems, political instability, and climate-related stressors. Early substance use elevates lifetime risks of mortality and morbidity, and is linked to HIV acquisition, traffic accidents, intimate partner violence, unemployment, and progression to substance use disorders. Meanwhile, the internalization of traditional gender norms — what researchers call inequitable gender beliefs — is established early in adolescence and reinforced throughout youth, and it frequently co-occurs with substance use. Both are independently associated with intimate partner violence, sexually transmitted infections, and poor mental health, suggesting that they may share underlying social drivers that a well-designed intervention could address together rather than one at a time.
What makes PEGISUS distinctive is its insistence on treating the peer group, not the individual, as the unit of change. Participants are recruited through an index case who enrolls two to five of their own peers with whom they already use substances — specifically, people who report weekly substance use or at least monthly binge drinking with peers over the previous three months. This deliberate social architecture reflects decades of research showing that peers play a decisive role in the initiation and escalation of substance use, and that most existing interventions, which focus narrowly on individual behavior, neglect the social and environmental forces that sustain risky patterns. Recent reviews suggest peer-focused mental health interventions have rarely been tested at all in low- and middle-income countries, and a prior South African friendship-group study showed decreases in certain gender-related practices and alcohol use only among female groups, leaving a substantial evidentiary gap that this new trial aims to fill.
The trial’s setting within vocational training programs is equally consequential. In South Africa, 35 percent of youth aged 15 to 24 are neither employed nor in school; in Zimbabwe, the figure is 36 percent, and in Zambia 29 percent. Vocational training offers an alternative pathway to economic opportunity for young people who have not completed formal schooling, but substance use and inequitable gender beliefs may undermine those benefits through their associations with dropout, unemployment, and violence. The study partners — Build It International in Zambia, Masvingo Polytechnic in Zimbabwe, and the Sozo Foundation in South Africa — offer training in fields ranging from bricklaying and welding to hairstyling and coding. By embedding the intervention into these programs and having program staff deliver it, the researchers hope to solve two chronic problems in global mental health: the enormous treatment gap, with an estimated 95 percent of young people needing substance use care not receiving it, and the sustainability problem of interventions that vanish once research funding ends.
Technically, the intervention builds on two established evidence-based programs: RAD-PAL, a brief substance use intervention, and Manhood 2.0, a gender equity curriculum. The eight sessions, each roughly ninety minutes, are activity-based and delivered to entire peer groups together, covering substance use, gender, and building healthy relationships. Formative work shaped the content through twelve focus group discussions with 97 young people, feedback from youth advisory boards in each country, and a pilot with 18 peer groups involving 57 participants. Interventionists — employees of the vocational training programs themselves — undergo training in good clinical practice, motivational interviewing, group facilitation, and handling distressed participants, supported by two levels of ongoing supervision including clinical oversight designed to prevent burnout among non-specialist providers. All sessions are audio-recorded, and fidelity is assessed with a session-specific checklist rating each component on a three-point scale.
The trial’s methodological rigor is a selling point in itself. Peer groups are randomized 1:1, stratified by country, using concealed allocation in REDCap, with the comparison arm receiving the standard vocational training program plus a referral for substance use services. Assessments occur at baseline, 12 weeks, and 24 weeks, with the primary outcome being the between-group difference in change on the total substance use involvement score of the World Health Organization’s Alcohol, Smoking and Substance Involvement Screening Test, or ASSIST. Younger participants aged 16 and 17 complete an adapted version, the ASSIST-Y. Secondary outcomes include substance-specific ASSIST scores, changes in gender equitable beliefs measured by the 23-item Gender Equitable Men’s Scale, and — notably — vocational training attendance and completion rates, employment status, and income earned at 24 weeks. The sample size calculations assume a standardized net mean difference of −0.5, drawn from a meta-analysis of brief behavioral interventions for youth substance use, an intra-class correlation of 0.08, and an average cluster size of four, yielding 95 percent power at a two-sided significance level of 0.05.
Analysis will follow CONSORT guidelines and modified intention-to-treat principles using linear mixed-effects models with cluster-specific random effects, adjusted for baseline scores, sex, and age. Superiority will be demonstrated if the lower bound of the 95 percent confidence interval for the between-group mean difference exceeds zero. An exploratory interaction test will probe whether intervention effects differ across the three countries, though the researchers caution that such tests are typically underpowered. Sensitivity analyses with multiple imputation are planned if more than roughly five percent of primary endpoints are missing. The team’s prior trials with similar populations report attrition below 10 percent, aided by rapport-building with community-based research assistants who remain blinded to intervention arm.
The ethical architecture of the study reflects the sensitivity of working with minors, illegal substance use, and gender-related content in contexts where same-sex relations remain criminalized. Participants under 18 require caregiver consent before providing assent, and parental consent forms deliberately frame the study around general substance use risk rather than disclosing individual selection criteria, to reduce the risk of family conflict or violence. Screening occurs separately for individuals within peer groups to ensure voluntary participation free of peer coercion, and group ground rules plus facilitator training aim to manage disagreements that may arise when discussing gender beliefs in mixed groups. In Zambia and Zimbabwe, participants are asked not to disclose sexual or gender minority identities, with interventionists trained to navigate these topics with cultural sensitivity while prioritizing participant safety and dignity within local legal frameworks. Adverse events must be reported within 24 hours and assessed against standardized criteria, with referrals available to local clinicians at every site.
If PEGISUS proves effective, the implications could ripple far beyond the 264 participants. The design tackles socioeconomic adversity head-on by pairing behavioral change with tangible employment pathways, and its delivery model — run by existing program staff within institutions that already serve the target population — offers a plausible route to scale and sustainability that most clinic-based interventions lack. The researchers acknowledge limitations, including potential homophily from index participants recruiting similar peers, the impossibility of blinding participants in a behavioral intervention, and a six-month follow-up window too short to capture longer-term employment effects. Yet the trial represents the first known study in Southern Africa to test an integrated intervention for substance use and gender equity beliefs delivered through vocational training. For a continent where more than half the population is under 24, and where young people’s coping mechanisms are shaped by structural forces as much as personal choices, the outcome of this trial may help determine whether the next generation of prevention efforts treats the whole social world of young people — their friends, their beliefs, and their economic futures — as one inseparable system.
Subject of Research: A cluster randomized controlled trial testing a peer group intervention to reduce substance use and inequitable gender beliefs among young people in vocational training programs in Southern Africa
Article Title: Protocol for a cluster randomized controlled trial among young people and their peers to reduce substance use and inequitable gender beliefs in Southern Africa
Article References: Protocol for a cluster randomized controlled trial among young people and their peers to reduce substance use and inequitable gender beliefs in Southern Africa. (n.d.). https://doi.org/10.1186/s13722-026-00718-7
Image Credits: AI Generated
DOI: 10.1186/s13722-026-00718-7
Keywords: substance use, gender norms, peer intervention, young people, vocational training, cluster randomized trial, Southern Africa, Zambia, Zimbabwe, South Africa, ASSIST, gender equity
News Source: Ophelia Keating. (October 14, 2026). Peer Groups Take Center Stage in Bold Trial Targeting Substance Use and Gender Norms in Southern Africa. Scienmag.
