Universal Intervention as a Protective Shield Against Exposure to Substance Use: Long-Term Outcomes and Public Health Significance

Abstract

We examined universal preventive intervention effects on adolescents' exposure to opportunities for substance use and on illicit substance use in the long term. Public schools (N = 22) were randomly assigned to the Iowa Strengthening Families Program (ISFP) or a control condition. We used odds ratio (OR) calculations and structural modeling to test the effects of the ISFP in the 6th grade on exposure to substance use across adolescence, as well as on 12th-grade illicit substance use occurring via reductions in exposure. The ISFP was associated with reduced exposure to illicit substance use (1.25 < or = OR < or = 2.37) that was, in turn, associated with reduced 12th-grade substance use (2.87 < or = OR < or = 6.35). The ISFP also reduced the rate of increase in exposure across adolescence (B = -0.37; P < .001), which was associated with the likelihood of 12th-grade illicit substance use (B = 0.30; P = .021), with a significant indirect effect (B = -0.11; P = .048). The ISFP in the 6th grade reduced substance use through a "protective shield" of reduced exposure. The relative reduction rate was 49%, which suggests that universal prevention shields can contribute to significant reductions in illicit substance use among adolescents.