Methods: Local research teams in Mexico City, Guadalajara and Monterrey recruited a probability sample of 12 public middle schools from each city, stratified by whether they met for morning or afternoon classes. We randomized schools to three conditions: Culturally adapted kiR (kiR-A), Original kiR translated into Spanish (kiR-O), and a treatment as usual Control condition. Regular teachers were trained to implement the manualized kiR-A and kiR-O curricula to their students over a 3-4 month period. Consented students in 7th grade completed pretest and posttest questionnaires in the 2017-18 school year (pretest n=5,523). We tested the relative effectiveness of kiR-A versus both kiR-O and Controls with baseline adjusted regression models using FIML estimation to adjust for attrition (24%), accounting for school-level random effects (clustering). We estimated models separately by gender group, tested for significant gender differences in intervention effects using interactions, and also investigated whether intervention effects varied by the level of use of substances at pretest (risk moderation).
Results: Risk moderation interactions showed that females already using substances experienced relatively greater efficacy of kiR-A in reducing overall alcohol use, binge drinking and hard drug use. Males already experimenting with substances reported greater efficacy of kiR-A in constraining intoxication and cigarette use. Both males and females in kiR-A reported relatively more use of the central kiR drug resistance strategies from pretest to post-test (Explain why you decline a drug offer, Leave the situation, Avoid drug offers) as well as related alternatives commonly used in Mexico (Change the subject, make up an Excuse, Ignore the offer). Female and male kiR-A students reported an expanding repertoire of different drug resistance skills. kiR-A female and male students reported relative declines in violence victimization and perpetrating bullying, while kiR-A females reported less criminal violence.
Conclusions and Implications: Although there were some gender differences in the type of substance use impacted by the intervention, the culturally adapted version of kiR for Mexico produced desired effects on substance use, use of effective drug resistance strategies, and violence for both females and males. The cultural grounding of the intervention enhanced outcomes compared to the original version, showed applicability to both genders, and extended desired effects to the prevention of violence.