An Introduction to Baseline Target Moderated Mediation to Guide Decisions on Adapting Prevention Programs

Introduction: There is a growing interest in the baseline target moderated mediation design (BTMM), because it holds substantial promise for advancing our understanding of how and why preventive interventions work, and for whom. The BTMM design employs moderated mediation within a longitudinal intervention evaluation study (i.e., a randomized controlled trial), to test whether baseline levels of intervention targets moderate the impact of the intervention on change in that target, and whether change in those targets mediates causal impact of the intervention on health outcomes. In other words, this approach will help us answer the question of which preventive interventions work best for what groups, and why that might be so. In doing so, it also sheds light on the groups that do not benefit from our current preventive interventions, and why that might be so. This presentation will provide the audience with an introduction to the baseline target moderated mediation design, and how it can be used to guide our efforts to target and tailor preventive interventions to the needs of different populations.

We begin by summarizing the more basic baseline target moderation (BTM) design, and its extension in the BTMM model. We explain how prevention scientists can employ this design using existing data evaluating preventive interventions. We then discuss several potential patterns of moderation, including compensatory effects (those who need the intervention most benefit the most), “rich-get-richer” effects (those who need the intervention least benefit most), crossover effects (some participants benefit, while other participants may be harmed), and fully iatrogenic effects (where intervention effects are increasingly negative as levels of baseline protective factors vary). We explain the implications of these patterns of moderation for prevention strategies, and under which conditions and findings from the BTM and BTMM designs warrant revision of existing preventive interventions. We end with a brief introduction of the other presentations in this symposium and explain how their methods compare.

To summarize, this introductory talk is specifically designed to allow the audience to fully understand the BTM and BTMM design, setting the stage for a thorough discussion of the findings that will be presented in the rest of the symposium.