Methods: Six middle schools from each region were recruited and randomized to intervention (kiR) or control (treatment as usual) groups. Regular 7th-grade teachers were trained to deliver kiR with fidelity. Students (Mage = 12.4; 52% male) with parental consent completed pretest questionnaires in Fall 2018 and posttests in Spring 2019 (n=755 at pretest). We tested the efficacy of kiR with baseline adjusted regression models using full information maximum likelihood (FIML) estimation to address attrition (11%) and accounting for school-level random effects. In addition to main effects, we tested whether desired kiR program effects were stronger for students at elevated risk (already using the substance at pretest). Outcomes included last 30-day substance use, drug resistance strategies, and other attitudinal mediators (antecedents) of adolescent substance use behaviors.
Results: Students from Seville came from lower SES households and were consistently more engaged in substance use than the Santiago sample. Controlling for these SES differences (parental education, family financial strain), there were similarities and differences in the kiR intervention effects in Seville and Santiago. Both sites reported desired effects on overall alcohol use and alcohol intoxication. Seville alone showed desired effects on binge drinking and use of illicit drugs other than marijuana. There were no overall program effects on use of tobacco or inhalants. Tests of risk moderation found desired effects on marijuana use among Seville students already using marijuana at pretest, i.e. relatively reduced use compared to controls. Both Seville and Santiago students in kiR reported greater use of drug resistance strategies, although the specific strategies varied. Scattered and site-specific desired effects on other mediators included effects in Santiago on less perceived substance use by schools peers and fewer substance offers, and effects in Seville showing increased drug refusal efficacy and negative substance use expectancies.
Conclusions: In a pilot test in two distinct regions, the culturally adapted version of kiR for middle school students in Spain reduced alcohol use, strengthened drug resistance skills, and constrained marijuana use among the adolescents most at-risk. Adapted kiR shows promise as a foundation for wider implementation and testing in Spain.