On Partial Identification of the Natural Indirect Effect

Journal of Causal Inference

article

Caleb Miles¹  Phyllis Kanki²  Seema Meloni²  Eric Tchetgen Tchetgen³ 

[1] Division of Biostatistics, University of California at Berkeley;Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health;Department of Biostatistics, Harvard T.H. Chan School of Public Health

关键词: cross-world counterfactual;    mediation;    partial identification;    single world intervention graph;    natural indirect effect;   

DOI  :  10.1515/jci-2016-0004

来源: De Gruyter

【 摘 要 】

In causal mediation analysis, nonparametric identification of the natural indirect effect typically relies on, in addition to no unobserved pre-exposure confounding, fundamental assumptions of (i) so-called “cross-world-counterfactuals” independence and (ii) no exposure-induced confounding. When the mediator is binary, bounds for partial identification have been given when neither assumption is made, or alternatively when assuming only (ii). We extend existing bounds to the case of a polytomous mediator, and provide bounds for the case assuming only (i). We apply these bounds to data from the Harvard PEPFAR program in Nigeria, where we evaluate the extent to which the effects of antiretroviral therapy on virological failure are mediated by a patient’s adherence, and show that inference on this effect is somewhat sensitive to model assumptions.

【 授权许可】

CC BY