package (Dinno, 2018) in R. We conducted the parallel analysis using the mixed correlation matrix, n set to the number of rows in the imputed data, and 1000 iterations. We constructed PCs to be orthogonal to the PRS by extracting the residual from the regression of each PC on the polygenic score ( resid(PRS ~ PC) ). The residuals from this series of linear models were used as covariates in subsequent analyses and are referred to as “phenotypic PCs” throughout the rest of this text.
