are assumed to be constructed from observed confounders that act as proxies for the correlated error structure in the model driven by both measured and unmeasured factors. Under these assumptions, inclusion of the PCs of measured confounders as covariates may reduce the effect of unmeasured confounders. We propose this solution to reduce collider bias when the correlation between PRS and environment is not driven by passive rGE (i.e., correlation between the genotypes that parents transmit to their children that are also associated with the type of rearing environment parents provide). In cases of passive rGE, directly controlling for confounders that drive this correlation is feasible and sufficient.
