Can Intersectoral Interventions Reduce Substance Use in Adolescence? Evidence From a Multicentre Randomized Controlled Study

This multicentre randomised controlled study evaluated a 3-year intersectoral intervention designed to reduce alcohol, tobacco, and cannabis use among adolescents in a tri-border region of Brazil, Argentina, and Paraguay. The intervention brought together 23 institutions from education, community, and social sectors and involved 880 adolescents, with treatment and control groups randomly assigned. Students in the treatment group were actively involved in co-developing prevention activities, while both groups later participated in the implemented activities.

Key findings show that adolescents who co-developed activities were significantly less likely to use substances: they were about 8 percentage points less likely to use tobacco and cannabis and 13 percentage points less likely to use alcohol compared to peers who only participated in activities (all statistically significant). Among those who used cannabis, frequent use was also lower in the co-development group. Peer consumption patterns were a strong predictor of individual use, underscoring the influence of social networks. 

The study highlights that participatory, multi-sector collaboration, especially involving young people in designing interventions, can meaningfully reduce substance use during adolescence—an important developmental period for long-term health