The pipeline for extracting and processing DNA as well as steps taken to ensure quality control are described in detail in Iacono et al. (2014) and in Miller et al. (2012). PCA was conducted on genotypes of non-Caucasian subjects using EIGENSTRAT (Price et al., 2006) in order to identify the major dimensions of genetic variation. Scores on the first 10 components were subsequently used in all analyses in order to control confounding due to any residual population stratification in allele frequencies (cf. Price et al., 2006).
