I have a quick question. In a seminar talk by Cathryn Lewis (professor of Genetic Epidemiology and Statistics at King's College London), she said that when you run a regression using Polygenic Risk Score (PRS) as your Independent Variable (IV) predicting your phenotype of interest (Dependent Variable - DV), you can add covariates to control for. These are normally principal components, genotyping batch, anything that it is correlated with your PRS, as opposed to covariates, such as age and IQ, that are correlated with the phenotype (i.e., DV) instead.
I was looking for a paper to check that I actually understood properly and to use as a reference instead of the seminar talk, but I couldn't find any. So I was wondering if you could confirm that it is common practice to correct for covariates associated with your genetic IV only, and/or if you have a paper to recommend.
Thanks so much, Silvia