with C1iEi. Alternatively, if C1 is socioeconomic status, subtle stratification not captured by self-report ethnicity, or a gene-environment correlation, may cause a relationship between the genetic polymorphism and C1, again leading to the GiEi term being confounded with the C1iEi term. In either case, the model in Equation (1) will properly control for such alternative explanations, and βG×E will be estimated correctly in the presence of βC1×E.
