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Abstract：
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-countterfactuals\" 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.
摘要：
在因果调解分析中，自然间接效应的非参数识别通常依赖于，除了没有未观察到的暴露前混淆，（i）所谓的“跨世界-计数”独立性和（ii）没有暴露引起的混杂因素的基本假设。当中介是二进制的，当没有做出任何假设时，已经给出了部分识别的界限，或者当仅假设(Ii)时。我们将现有的界限扩展到多体介体的情况，并为仅假设（i）的情况提供界限。我们将这些界限应用于尼日利亚哈佛PEPFAR计划的数据，我们评估抗逆转录病毒治疗对病毒学失败的影响是由患者的依从性介导的程度，并表明对这种效应的推断对模型假设有些敏感。
