“…Systematic differences might exist in genotypes due to population stratification, yet 15 reviewed studies did not consider this issue in their analyses. Among the other 14 studies, principal coordinate analysis was the most frequently used approach to identify geographic ancestry and control for population stratification Cleveland, Griffin, et al, 2018;Lemery-Chalfant et al, 2018;Russell et al, 2018;Schlomer et al, , 2017Schlomer et al, , 2019Shaw et al, 2019;Vandenbergh et al, 2016). Two studies from the Fast Track program conducted separate analyses for the European-American and the African-American subsamples (Albert, Belsky, Crowley, Bates, et al, 2015;Zheng et al, 2018); Chhangur et al (2017) included ethnicity as a covariate, and Beach, Lei, Brody, & Philibert (2017) included ancestry information as a control variable for the population stratification.…”