标题： 重新表述跨世界独立性以识别路径特定效应 显示英文标题

标题： Reframing cross-world independence for identifying path-specific effects

摘要： 理解复杂系统中的因果机制需要在多中介模型中评估路径特定效应（PSEs）。传统上，PSEs的识别依赖于要求严格的跨世界独立性假设。为了放松这一假设，VanderWeele等人（2014）提出了一种干预方法，重新定义了PSEs，而Stensrud等人（2021）则引入了可忽略的组件条件，以在竞争风险下识别可分离效应。在本研究中，我们利用SWIGs来剖析这三种语义的因果基础，并取得两个关键进展。首先，我们将可分离效应从竞争风险推广到多中介模型的设置，并推导出其识别所需的假设。其次，我们通过澄清它们如何不同地解释反事实结果来统一三种方法：作为中介驱动效应（经典）、随机对比（干预）或组件特定行动（可分离）。我们进一步证明，跨世界独立性的违反源于模型中遗漏的中介变量。类比于混杂控制，我们认为正如通过条件化足够混杂因素可以实现交换性一样，跨世界独立性可以通过包含足够多的中介变量来近似。这种重新表述将一个抽象假设转化为一种具体的建模策略，为复杂因果系统中的应用中介分析提供了更实际的前进路径。 显示英文摘要

摘要： Understanding causal mechanisms in complex systems requires evaluating path-specific effects (PSEs) in multi-mediator models. Identification of PSEs traditionally relies on the demanding cross-world independence assumption. To relax this, VanderWeele et al. (2014) proposed an interventional approach that redefines PSEs, while Stensrud et al. (2021) introduced dismissible component conditions for identifying separable effects under competing risks. In this study, we leverage SWIGs to dissect the causal foundations of these three semantics and make two key advances. First, we generalize separable effects beyond competing risks to the setting of multi-mediator models and derive the assumptions required for their identification. Second, we unify the three approaches by clarifying how they interpret counterfactual outcomes differently: as mediator-driven effects (classical), randomized contrasts (interventional), or component-specific actions (separable). We further demonstrate that violations of cross-world independence originate from mediators omitted from the model. By analogy to confounder control, we argue that just as exchangeability is achieved by conditioning on sufficient confounders, cross-world independence can be approximated by including sufficient mediators. This reframing turns an abstract assumption into a tangible modeling strategy, offering a more practical path forward for applied mediation analysis in complex causal systems.