We then fit a series of linear models to test the impact of the phenotypic PCs on the estimate of the effect of PRS on AUD Sx. Models were tested with 10 ancestry PCs for a total of 3 linear models for each collider variable. Model B1. AUD Sx ~ PRS + Ancestry PCsModel B2. AUD Sx ~ PRS + Ancestry PCs + Collider VariableModel B3. AUD Sx ~ PRS + Ancestry PCs + Collider Variable + Phenotypic PCs The presence of collider bias is inferred from the decrease in the partial effect size of the PRS in the presence of the heritable collider variable; for example, if the PRS effect decreases from model B1 to B2. A correction for this bias is identified when the partial effect size of the PRS increases in the presence of PC covariates; for example, if the PRS effect increases from model B2 to B3. We present change in β and R2 between models in their original scale and as a percentage of the model B1 effect size.
