Abstract
PURPOSE: An earlier randomized controlled study found that a universal, family-focused preventive intervention produced protective shield effects-reduced adolescent exposures to illicit substance opportunities-among adolescents in grade 12. This study examined a follow-up assessment of the sample during young adulthood. METHODS: A randomized controlled trial evaluated the Iowa Strengthening Families Program that was implemented in 22 rural schools (N = 446 families) when the participants were in grade six. Measures included adolescent exposure to illicit substance use and young adult lifetime substance use (age 21; N = 331). Growth curve modeling examined indirect intervention effects through growth factors of adolescent exposure. RESULTS: Findings from this study confirm protective shield effects that mediate long-term reduction of illicit substance use (β = -.14, p = .02, Relative Reduction Rate = 28.2%). CONCLUSIONS: The benefits of decreasing exposure to substance use during adolescence through universal interventions were supported, with positive effects extending into young adulthood.