A large majority (87 percent) of participants were born in Scotland and 95 percent in the United Kingdom. Roughly 82 percent of parents and 75 percent of grandparents were also born in Scotland. Up to 99 percent of participants defined their ethnicity as ‘white’ (Smith et al. 2013). Multi‐dimensional scaling (MDS) components were created according to the ENIGMA 1000 genomes protocol (ENIGMA 2013) in the software package PLINK (Purcell et al. 2007). A plot of the first and second MDS components showing the genotyped individuals in GS:SFHS and 11 different ethnic HapMap populations is shown in Supporting Information Fig. S1. The GS:SFHS individuals cluster tightly with the HapMap CEU population and show little admixture with the other ethnic populations. Four MDS components were used to correct for population stratification.
