In this paper, we study the impact of unmeasured confounding on inference about a two-way interaction in a mean regression model with identity, log or logit link function. Necessary and sufficient conditions are established for a two-way interaction to be nonparametrically identified from the observed data, despite unmeasured confounding for the factors defining the interaction. A lung cancer data application illustrates the results.
Tchetgen Tchetgen, Eric J. and VanderWeele, Tyler J., "Robustness of Measures of Interaction to Unmeasured Confounding" (March 2012). COBRA Preprint Series. Working Paper 89.