In order to avoid any spurious results due to population stratification (Cardon & Palmer, 2003), the target sample for these analyses was comprised of non-Hispanic White individuals only. Self-reported White individuals who provided DNA and passed quality control procedures were the largest racial segment (N = 341, 56%) of those who provided DNA. Genomic principal components analysis (see Genotyping Procedures) within this group identified four ancestral outliers who were removed from analysis (sigma > 6.0), resulting in a final sample size for enrichment analysis of N = 337. A comparison of these participants versus non-Hispanic White participants who did not provide DNA and W11 survey data or pass quality control procedures is reported in the Results.
