Methods: Local research teams in Mexico City, Guadalajara, and Monterrey recruited a stratified probability sample of 36 middle schools, 12 in each city. We randomized schools to three conditions: Culturally adapted kiR (kiR-A), Original kiR translated into Spanish (kiR-O), and a Control condition with treatment as usual. Regular teachers were trained to implement the curricula over a 3-4 month period. All 7th grade students with parental consent completed pretests in Fall 2017 (n=5,524), and three subsequent posttests: later in 7th grade (T2), in 8th (T3) and 9th grade (T4). The relative effectiveness of kiR-A versus both kiR-O and Control was analyzed through auto-regressive path models in Mplus using FIML estimation to adjust for attrition and accounting for school and city-level random effects.
Results: kiR-A students who had used alcohol at baseline reported significantly lower odds of using alcohol over time compared to the Control students (T2: OR=.65, p=.003; T4: OR= .65, p=.019) and kiR-O students (T2: OR=.70, p=.074; T4: OR=0.64, p=.004). Short-term effects were also seen among users at baseline in the odds of using cigarettes between kiR-A students and Control students (T2: OR=0.54, p=.03). There were no significant differences between Control and kiR-O students in the odds of using alcohol or cigarettes over time.
Conclusions & Implications: For students with prior involvement in substance use, having a culturally adapted curriculum is efficacious for preventing subsequent alcohol use over time, the most commonly used substance in Mexico. The efficacious of a culturally adapted curriculum is above and beyond that of a linguistically adapted curriculum. For more at-risk adolescents, simply translating an efficacious prevention intervention from English into Spanish, may not enough to prevent and reduce substance use in contexts outside the United States.