Estimating Treatment Effects in Networks under Unknown Exposure Mappings

Abstract

Estimating heterogeneous treatment effects in network settings is complicated by interference, meaning that the outcome of an instance can be influenced by the treatment status of others. Existing causal machine learning approaches that account for interference usually rely on a prespecified exposure mapping that summarizes how others' treatments affect the outcome of a given instance, a simplification that is often inappropriate. We propose HINet, a neural method that combines an expressive GNN outcome model with network-aware domain-adversarial training. The outcome model learns an exposure-relevant neighborhood representation jointly with outcome prediction, allowing HINet to capture heterogeneous interference without prespecifying an exposure mapping. HINet's adversarial component uses both node and neighborhood information to promote balance in the learned representations with respect to treatment assignment. We further derive a population-level generalization bound and introduce two metrics for evaluation across counterfactual networks. An empirical evaluation on synthetic and semi-synthetic network datasets demonstrates that HINet performs consistently across diverse exposure mappings, while methods based on a prespecified mapping can perform poorly when it is misspecified.