Effects of Exposure to the Communities That Care Prevention System on Youth Problem Behaviors in a Community-Randomized Trial: Employing an Inverse Probability Weighting Approach.

Earlier intention-to-treat (ITT) findings from a community-randomized trial demonstrated effects of the Communities That Care (CTC) prevention system on reducing problem behaviors among youth. In ITT analyses, youth were analyzed according to their original study community's randomized condition even if they moved away from the community over the course of follow-up and received little to no exposure to intervention activities. Using inverse probability weights (IPWs), this study estimated effects of CTC in the same randomized trial among youth who remained in their original study communities throughout follow-up. Data were from the Community Youth Development Study, a community-randomized trial of 24 small towns in the United States. A cohort of 4,407 youth was followed from fifth grade (prior to CTC implementation) to eighth grade. IPWs for one's own moving status were calculated using fifth- and sixth-grade covariates. Results from inverse probability weighted multilevel models indicated larger effects for youth who remained in their study community for the first 2 years of CTC intervention implementation compared to ITT estimates. These effects included reduced likelihood of alcohol use, binge drinking, smokeless tobacco use, and delinquent behavior. These findings strengthen support for CTC as an efficacious system for preventing youth problem behaviors.