Objective. To examine the effects of a delivery system for evidence-based preventive interventions through 12th grade, 6.5 years past baseline. Method. A cohort sequential design included 28 public school districts randomly assigned to the partnership delivery system or usual-programming conditions. At baseline, 11,960 students participated. Partnerships supported community teams that implemented a family-focused intervention in 6th grade and a school-based intervention in 7th grade. Outcome measures included lifetime, current misuse, and frequencies of misuse, for a range of substances. Intent-to-treat, multilevel analyses of covariance of point-in-time misuse and analyses of growth in misuse were conducted. Results. Results showed significantly lower substance misuse in the intervention group at one or both time points for most outcomes, with relative reduction rates of up to 31.4%. There was significantly slower growth in misuse in the intervention group for 8 of the 10 outcomes. In addition, risk moderation results indicated that there were significantly greater intervention benefits for higher- versus lower-risk youth, for the misuse of 6 of the 10 substances at 11th grade, illicit substances at 12th grade, and growth in the misuse of illicit substances. Conclusion. Partnership-based delivery systems for brief universal interventions have potential for public health impact by reducing substance misuse among youth, particularly higher-risk youth. (c) 2013 Elsevier Inc. All rights reserved.
