An introduction to mediation analyses of randomized controlled trials.

Mediation analyses of randomized controlled trials can be used to investigate the mechanisms by which health interventions cause outcomes. In this article we provide a brief introduction to mediation analysis in the context of randomized controlled trials. We introduce common target effects, causal assumptions, estimation approaches, and illustrate these concepts using a published mediation analysis of the Systolic Blood Pressure Intervention Trial. Well-conducted mediation analyses of randomized trials can provide meaningful insights to guide clinical and policy decisions.