Statistical methods in medical research
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Stat Methods Med Res · Feb 2012
ReviewA review of causal estimation of effects in mediation analyses.
We describe causal mediation methods for analysing the mechanistic factors through which interventions act on outcomes. A number of different mediation approaches have been presented in the biomedical, social science and statistical literature with an emphasis on different aspects of mediation. We review the different sets of assumptions that allow identification and estimation of effects in the simple case of a single intervention, a temporally subsequent mediator and outcome. ⋯ The understanding of such assumptions is crucial since some can be assessed under certain conditions (e.g. treatment-mediator interactions), whereas others cannot (sequential ignorability). These issues become more complex with multiple mediators and longitudinal outcomes. In addressing these assumptions, we review several causal approaches to mediation analyses.