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Natural direct and indirect effects on the exposed: effect decomposition under weaker assumptions
Stijn Vansteelandt1, Tyler J Vanderweele
1Department of Applied Mathematics and Computer Sciences, Ghent University, Krijgslaan 281 S9, 9000 Ghent, Belgium. stijn.vansteelandt@ugent.be
Biometrics
|September 20, 2012
Summary
This study introduces natural direct and indirect effects on the exposed, enabling effect decomposition under weaker conditions than population effects. These new measures are valuable for causal inference, especially with exposure-induced mediator confounding.
Area of Science:
- Causal inference
- Epidemiology
- Biostatistics
Background:
- Traditional causal inference methods struggle with exposure-induced mediator-outcome confounding.
- Existing approaches for natural direct and indirect effects have limitations in identification conditions.
Purpose of the Study:
- To define and identify natural direct and indirect effects on the exposed.
- To establish weaker identification conditions compared to population-level effects.
- To address limitations in causal effect decomposition with mediator confounding.
Main Methods:
- Development of novel definitions for natural direct and indirect effects on the exposed.
- Analysis of identification conditions, including scenarios with and without exposure-affected confounders.
- Introduction of a selection-bias function for complex identification scenarios.
Main Results:
- Natural direct and indirect effects on the exposed allow for effect decomposition under weaker conditions.
- Identification is achievable under similar conditions to controlled direct effects when confounders are not exposure-affected.
- Identification is possible with a selection-bias function in more complex scenarios.
Conclusions:
- Natural direct and indirect effects on the exposed offer a valuable tool for causal inference.
- These effects are of intrinsic interest and applicable in various research settings.
- The findings extend causal inference capabilities to address previously intractable confounding scenarios.
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