This study estimated sustained impacts and long-term benefits and costs of the Communities That Care (CTC) prevention system, implemented and evaluated in a longitudinal cluster-randomized trial involving 24 communities in seven states. Analyses utilized reports from a longitudinal panel of 4407 participants, followed since the study's baseline in grade 5, with most recent follow-up 12 years later at age 23. Impacts on lifetime abstinence from primary outcomes of substance use and antisocial behavior were estimated using generalized linear mixed Poisson regression analysis, adjusted for individual and community-level covariates. Possible cascading effects on 4-year college completion, major depressive disorder, and generalized anxiety disorder through age 23 were evaluated as secondary outcomes. CTC had a statistically significant global effect on primary outcomes and also on combined primary and secondary outcomes. Among primary outcomes, point estimates suggested absolute improvements in lifetime abstinence of 3.5 to 6.1% in the intervention arm and relative improvements of 13 to 55%; 95% confidence intervals revealed some uncertainty in estimates. Among secondary outcomes, 4-year college completion was 1.9% greater among young adults from intervention communities, a 20% relative improvement. Mental health outcomes were approximately the same across trial arms. Although CTC had small sustained effects through age 23, benefit-cost analyses indicated CTC was reliably cost beneficial, with a net present value of $7152 (95% credible interval: $1253 to $15,268) per participant from primary impacts and $17,919 ($306 to $39,186) when secondary impacts were also included. It remained cost beneficial even when impacts were adjusted downward due to the involvement of CTC's developer in the trial. Findings suggest that broader dissemination of CTC could improve public health and individual lives in the long term and generate positive net benefits to society.
Keywords: Benefit–cost analysis; Communities That Care; Long-term impacts.