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Updated: May 23, 2026

A Modified Trier Social Stress Test for Vulnerable Mexican American Adolescents
Published on: July 10, 2017
Benefits of universal intervention effects on a youth protective shield 10 years after baseline
Richard L Spoth1, Linda S Trudeau, Max Guyll
1Partnerships in Prevention Science Institute, Iowa State University, Ames, IA, USA. rlspoth@iastate.edu
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.
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