Towards identifiability of micro total effects in summary causal graphs with latent confounding: extension of the front-door criterion

TL;DR

This paper extends causal inference methods to partially specified summary causal graphs in dynamic systems, providing conditions for identifying total effects despite latent confounding and cycles.

Contribution

It introduces new graphical conditions for identifying total effects in summary causal graphs with latent confounding and cycles, expanding the front-door criterion.

Findings

Provides sufficient conditions for effect identification in complex graphs

Addresses challenges of latent confounding and cycles in dynamic systems

Extends causal inference tools to partially specified, evolving systems

Abstract

Conducting experiments to estimate total effects can be challenging due to cost, ethical concerns, or practical limitations. As an alternative, researchers often rely on causal graphs to determine whether these effects can be identified from observational data. Identifying total effects in fully specified causal graphs has received considerable attention, with Pearl's front-door criterion enabling the identification of total effects in the presence of latent confounding even when no variable set is sufficient for adjustment. However, specifying a complete causal graph is challenging in many domains. Extending these identifiability results to partially specified graphs is crucial, particularly in dynamic systems where causal relationships evolve over time. This paper addresses the challenge of identifying total effects using a specific and well-known partially specified graph in dynamic systems called a summary causal graph, which does not specify the temporal lag between causal relations and can contain cycles. In particular, this paper presents sufficient graphical conditions for identifying total effects from observational data, even in the presence of cycles and latent confounding, and when no variable set is sufficient for adjustment.