School Drug Prevention Program Reduced Marijuana Use Among Brazilian Teens Aged 13-15 | Research

The takeaway

A European school-based drug prevention program adapted for Brazil showed evidence of reducing marijuana use among 13-15 year olds, with 85.7% of intervention participants who were using marijuana transitioning to non-use.

Read this if you work in school-based drug prevention or education policy.

85.7% of 13-15 year old marijuana users stopped using after the school program vs 28.6% of controls.

What the researchers found

Researchers evaluated the Unplugged program, a European school-based drug prevention curriculum, adapted for Brazilian public middle schools. The program had no measurable effect on 11-12 year olds, but showed promising results for 13-15 year olds.

Among 13-15 year old marijuana users, 85.7% in the intervention group transitioned from use to non-use, compared to only 28.6% in the control group (OR = 17.5). Students who received the program maintained their pre-program drug use levels, while control group students showed significant increases in marijuana use and binge drinking over the same period.

The program consisted of 12 weekly classes focused on life skills, social influence resistance, and knowledge about drugs.

Why it matters

Most Brazilian schools lack structured drug prevention programs. This study demonstrates that a well-designed, culturally adapted program can reduce marijuana use among teens in the age group most likely to initiate use. The striking difference in transition rates (85.7% vs 28.6%) suggests meaningful impact.

The numbers in context

2,185 students in 16 schools across 3 cities. 12 weekly program sessions. Among 13-15 year old marijuana users, 85.7% of intervention participants stopped using vs 28.6% of controls (OR = 17.5, p = 0.039).

How the study worked

Non-randomized controlled trial conducted in 2013 with 2,185 students across 16 public schools in 3 Brazilian cities. The intervention group received 12 weekly Unplugged classes; the control group received no prevention programming. Multilevel analyses assessed changes in drug consumption over time and between groups.

What this study cannot tell us

Non-randomized design introduces potential selection bias. The marijuana user subgroup was small, making the 85.7% vs 28.6% comparison less reliable despite statistical significance. Short follow-up period. The control schools had no prevention programming at all, which inflates the apparent effect size compared to an active control.

How to read the evidence

Preliminary evidence from a non-randomized trial with promising but small-subgroup results. The lack of randomization and small marijuana user sample size warrant caution.

When this study was published

Published in 2016. School-based prevention programs continue to be evaluated and refined.

The bigger picture

Drug prevention programs that focus on life skills and social influence resistance rather than scare tactics have shown the most consistent evidence of effectiveness. This study suggests such approaches can work across cultural contexts when properly adapted.

Questions still open

Would the effects persist beyond the study period? Would a randomized controlled trial confirm these findings? How much of the effect is due to the program versus attention and adult engagement? Would the program work in private schools or rural areas?

Common questions

Do school drug prevention programs work?

This study found that a skills-based program reduced marijuana use among 13-15 year olds in Brazil. Programs focused on life skills and resisting social pressure tend to be more effective than those relying on fear or information alone.

Why did the program only work for older teens?

The 11-12 year olds may have had too little drug exposure for prevention to show measurable effects, while the 13-15 year olds were in the age range where marijuana initiation typically begins, making prevention more relevant and measurable.

Read the original research

Efficacy evaluation of the school program Unplugged for drug use prevention among Brazilian adolescents.

BMC public health, 16(1), 1206

View on PubMed ↗

Citation

Sanchez, Zila M; Sanudo, Adriana; Andreoni, Solange; Schneider, Daniela; Pereira, Ana Paula D; Faggiano, Fabrizio. (2016). Efficacy evaluation of the school program Unplugged for drug use prevention among Brazilian adolescents.. BMC public health, 16(1), 1206.