Effectiveness of a School-Based Drug Prevention Program: Tú Decides 2.0.

Adolescent substance use remains a significant public health concern in Spain. This study evaluates the effectiveness of "Tú Decides 2.0," an updated school-based drug prevention program, in reducing substance use among Spanish adolescents. A nine-month, two-arm, quasi-experimental controlled trial was conducted involving 2251 adolescents (aged 12-17) from 13 secondary schools in three Spanish regions. The intervention group (n = 1209) received the "Tú Decides 2.0" program, while the control group (n = 1042) underwent only assessment sessions. Primary outcomes were past 30-day use of alcohol, tobacco, e-cigarettes, and cannabis at three-month follow-up. Overall, prevalence of use was lower than the national mean data. GEE analyses following an ITT approach showed significant effects of the program in reducing the prevalence of self-reported e-cigarette use in the intervention group compared to the control group in 2nd (OR = 0.54; CI = 0.32; 0.90) and 4th (OR = 0.33; CI = 0.27; 1.14) CSE years. Significant effects were also found in reducing the prevalence of alcohol (OR = 0.57; CI = 0.32; 1.00) and tobacco (OR = 0.57; CI = 0.37; 0.88) use at three-months follow-up among students in 2nd CSE year. No significant effects were observed for cannabis nor for the 1st and 3rd CSE years. Models conducted using Multiple Imputation yielded similar results. The "Tú Decides 2.0" program demonstrated effectiveness in reducing both the incidence and prevalence of e-cigarette, alcohol and tobacco use among Spanish adolescents. These findings support the implementation of updated, digitalized school-based interventions for substance use prevention.Trial Registration ClinicalTrials.gov Registry (#NCT05950074).