Evaluating a Method to Estimate Mediation Effects With Discrete-Time Survival Outcomes.

The utility of evaluating mediation effects spans across research domains. The model facilitates investigation of underlying mechanisms of event timing and, as such, has the potential to help strengthen etiological research and inform intervention work that incorporates the evaluation of mediating variables. In order for the analyses to be maximally useful however, it is critical to employ methodology appropriate for the data under investigation. The purpose of this paper is to evaluate a regression-based approach to estimating mediation effects with discrete-time survival outcomes. We empirically evaluate the performance of the discrete-time survival mediation model in a statistical simulation study, and demonstrate that results are functionally equivalent to estimates garnered from a potential-outcomes framework. Simulation results indicate that parameter estimates of mediation in the model were statistically accurate and precise across the range of examined conditions. Type 1 error rates were also tolerable in the conditions studied. Adequate power to detect effects in the model, with binary X and continuous M variables, required effect sizes of the mediation paths to be medium or large. Possible extensions of the model are also considered.

Improving Our Ability to Evaluate Underlying Mechanisms of Behavioral Onset and Other Event Occurrence Outcomes: A Discrete-Time Survival Mediation Model.

The purpose of this article is to introduce and describe a statistical model that researchers can use to evaluate underlying mechanisms of behavioral onset and other event occurrence outcomes. Specifically, the article develops a framework for estimating mediation effects with outcomes measured in discrete-time epochs by integrating the statistical mediation model with discrete-time survival analysis. The methodology has the potential to help strengthen health research by targeting prevention and intervention work more effectively as well as by improving our understanding of discretized periods of risk. The model is applied to an existing longitudinal data set to demonstrate its use, and programming code is provided to facilitate its implementation.

Randomized trial of a broad preventive intervention for Mexican American adolescents.

OBJECTIVE: This randomized trial of a family-focused preventive intervention for Mexican American (MA) adolescents evaluated intervention effects on adolescent substance use, internalizing and externalizing symptoms, and school discipline and grade records in 8th grade, 1 year after completion of the intervention. The study also examined hypothesized mediators and moderators of intervention effects. METHOD: Stratified by language of program delivery (English vs. Spanish), the trial included a sample of 516 MA adolescents (50.8% female; M = 12.3 years, SD = 0.54) and at least one caregiver that were randomized to receive a low-dosage control group workshop or the 9-week group intervention that included parenting, adolescent coping, and conjoint family sessions. RESULTS: Positive program effects were found on all 5 outcomes at 1-year posttest but varied depending on whether adolescents, parents, or teachers reported on the outcome. Intervention effects were mediated by posttest changes in effective parenting, adolescent coping efficacy, adolescent school engagement, and family cohesion. The majority of intervention effects were moderated by language, with a larger number of significant effects for families who participated in Spanish. Intervention effects also were moderated by baseline levels of mediators and outcomes, with the majority showing stronger effects for families with poorer functioning at baseline. CONCLUSION: Findings not only support the efficacy of the intervention to decrease multiple problem outcomes for MA adolescents but also demonstrate differential effects for parents and adolescents receiving the intervention in Spanish vs. English, and depending on their baseline levels of functioning.

Social support, discrimination, and coping as predictors of posttraumatic stress reactions in youth survivors of Hurricane Katrina.

This study examined the influence of aspects of the post-Hurricane Katrina recovery environment (i.e., discrimination, social support) and coping behaviors on children's posttraumatic stress reactions (symptoms of posttraumatic stress disorder [PTSD], anxiety, and depression). Data corresponding to 46 youth (M = 11.43 years; 39% girls; 33% African American, 67% European American) revealed that greater helpfulness from extrafamilial sources of social support predicted lower levels of child-rated symptoms of PTSD, anxiety, and depression. A positive predictive relation was found between helpfulness from professional support sources and PTSD, perhaps suggesting that parents whose children were experiencing higher PTSD symptom levels sought professional support and reported it to be helpful. Youths' avoidant coping behaviors predicted both PTSD and anxiety symptoms. Discrimination, active coping, and familial support did not predict any of the posttraumatic stress reactions assessed in this study.