Sensitivity Analysis for Causal Mediation and Path Analysis with the GMediation R Package

Oregon Convention Center 

Causal mediation analysis seeks to decompose a treatment or exposure effect into direct and indirect effects. Initially developed for a single mediator, this methodology has been extended to allow for multiple contemporaneous or causally ordered mediators. Generalized causal mediation and path analysis (GCMPA) provides a further extension by accommodating multiple mediators at each of two causally-ordered 'stages' with mediators and the final outcome following generalized linear models. As these methods rely on the untestable assumption of sequential ignorability, a sensitivity analysis is widely considered to be an important accompaniment to causal mediation analysis. Unfortunately, methods for sensitivity analysis are currently available only for the single mediation case. We present a new sensitivity analysis approach applicable to the GCMPA setting, thus, evaluating the effect of departures from sequential ignorability on estimated path-specific effects. We discuss implementation of this methodology in the recently developed GMediation R package, and illustrate using data from a study of causal pathways between socioeconomic status and adolescent dental caries.

causal inference

generalized linear models

path-specific effects

sequential ignorability 

Biometrics Section