because conventional confounding is typically low for single genetic variants, problems of selection bias will be less in this context.10 However, given the rapid growth in studies using data from highly selected samples such as UK Biobank, and the use of genetic risk scores rather than single genetic variants, we revisited this question and used simulation to explore the potential impact of even relatively weak effects on participation. Given empirical evidence of selection in cross-sectional and cohort studies, what is the potential impact of this on observed phenotypic and genotypic associations?
