Universality of Effects: An Examination of the Comparability of Long-Term Family Intervention Effects on Substance Use Across Risk-Related Subgroups

Abstract

This study extends earlier investigation of family risk-related moderation of two brief, family-focused preventive interventions. It examines effects on the trajectories of substance initiation over a period of six years after a pretest assessment, evaluating whether effects were comparable across higher- and lower-risk subgroups. The two interventions, designed for general-population families of adolescents, were the seven-session Iowa Strengthening Families Program (ISFP) and the five-session Preparing for the Drug Free Years program (PDFY). Thirty-three rural public schools were randomly assigned to either the ISFP, the PDFY, or a minimal contact control condition. Curvilinear growth curve analyses were used to evaluate the universality of intervention effectiveness by testing for risk moderation of intervention effects on school-level substance use trajectories of initiation of alcohol and illicit substance use. Results were most consistent with the interpretation that both interventions provided comparable benefits for both outcome measures, regardless of family risk status. Findings are discussed in terms of their implications for implementing universal preventive interventions in general populations.