Assessing Interactive Causes of an Occurred Outcome Due to Two Binary Exposures

TL;DR

This paper develops a method to assess the interactive causal effects of two binary exposures on a binary outcome, using posterior probabilities and secondary outcomes, with application to smoking and asbestos exposure in lung cancer.

Contribution

It introduces a novel approach to identify and quantify the interactive causes of an observed outcome using posterior probabilities and secondary outcomes.

Findings

The method successfully identifies the primary cause as the interaction between smoking and asbestos.

Application to lung cancer shows the disease is mainly due to the synergistic effect.

The approach enhances causal attribution analysis for binary exposures and outcomes.

Abstract

In contrast to evaluating treatment effects, causal attribution analysis focuses on identifying the key factors responsible for an observed outcome. For two binary exposure variables and a binary outcome variable, researchers need to assess not only the likelihood that an observed outcome was caused by a particular exposure, but also the likelihood that it resulted from the interaction between the two exposures. For example, in the case of a male worker who smoked, was exposed to asbestos, and developed lung cancer, researchers aim to explore whether the cancer resulted from smoking, asbestos exposure, or their interaction. Even in randomized controlled trials, widely regarded as the gold standard for causal inference, identifying and evaluating retrospective causal interactions between two exposures remains challenging. In this paper, we define posterior probabilities to characterize the interactive causes of an observed outcome. We establish the identifiability of posterior probabilities by using a secondary outcome variable that may appear after the primary outcome. We apply the proposed method to the classic case of smoking and asbestos exposure. Our results indicate that for lung cancer patients who smoked and were exposed to asbestos, the disease is primarily attributable to the synergistic effect between smoking and asbestos exposure.