We then used EIGENSTRAT (Price et al., 2006) in order to address any residual population stratification and to identify ancestral outliers. Genomic principal components were extracted within the self-reported non-Hispanic White sample. Default parameters were used in accordance with recommendations for this procedure (Turner et al., 2011), and data was linkage disequilibrium pruned (r2 < 0.5) prior to extraction in order to reduce computational burden. Iterative extraction identified four individuals who were ancestral outliers relative to the rest of the self-reported White sample (sigma > 6.0); these four individuals were removed, resulting in a final analysis sample after all quality control procedures of N = 337.
