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This Article Figures Only Full Text Full Text (PDF) All Versions of this Article: AJPH.2007.133298v1 99/11/2026    most recent Submit a response View Shopping Cart Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Spoth, R. Articles by Shin, C. PubMed PubMed Citation Articles by Spoth, R. Articles by Shin, C. Related Collections Epidemiology Adolescent Health Prevention Public Health Practice Other Child and Adolescent Health Alcohol Drugs

Richard Spoth, PhD, Max Guyll, PhD and Chungyeol Shin, PhD

Richard Spoth and Chungyeol Shin are with the Partnerships in Prevention Science Institute, Iowa State University, Ames. Max Guyll is with the Department of Psychology at Iowa State University.

Correspondence: Correspondence should be sent to Richard Spoth, Partnerships in Prevention Science Institute (http://www.ppsi.iastate.edu), ISU Research Park, Building 2, Suite 2500, 2625 North Loop Drive, Iowa State University, Ames, Iowa 50010 (rlspoth{at}iastate.edu). Reprints can be ordered at http://www.ajph.org by clicking on the "Reprints/Eprints" link. The authors had no conflicts of interest to report.

Objectives. We examined universal preventive intervention effects on adolescents' exposure to opportunities for substance use and on illicit substance use in the long term.

Methods. 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.

Results. The ISFP was associated with reduced exposure to illicit substance use (1.25 OR 2.37) that was, in turn, associated with reduced 12th-grade substance use (2.87 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).

Conclusions. 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.