An application of the Complier Average Causal Effect analysis to examine the effects of a family intervention in reducing illicit drug use among high-risk Hispanic adolescents.

The Complier Average Causal Effect (CACE) method has been increasingly used in prevention research to provide more accurate causal intervention effect estimates in the presence of noncompliance. The purpose of this study was to provide an applied demonstration of the CACE analytic approach to evaluate the relative effects of a family-based prevention intervention, Familias Unidas, in preventing/reducing illicit drug use for those participants who received the intended dosage. This study is a secondary data analysis of a randomized controlled trial designed to evaluate the relative efficacy of Familias Unidas with high-risk Hispanic youth. A total of 242 high-risk Hispanic youth aged 12-17 years and their primary caregivers were randomized to either Familias Unidas or Community Practice and assessed at baseline, 6 months and 12 months postbaseline. CACE models were estimated with a finite growth mixture model. Predictors of engagement were included in the CACE model. Findings indicate that, relative to the intent-to-treat (ITT) analytic approach, the CACE analytic approach yielded stronger intervention effects among both initially engaged and overall engaged participants. The CACE analytic approach may be particularly helpful for studies involving parent/family-centered interventions given that participants may not receive the intended dosage. Future studies should consider implementing the CACE analysis in addition to ITT analysis when examining the effects of family-based prevention programs to determine whether, and the extent to which, the CACE analysis has more power to uncover intervention effects.