principal components calculated using EIGENSTRAT (Miller et al., 2012). In all, genotypic and phenotypic data were available for 7224 participants (Table 1.), comprising 3849 parent participants, 2916 twins (1901 monozygotic, 1015 dizygotic), and 459 non-parental SIBS participants. Only participants who had ever tried alcohol in their life were included in subsequent analyses (N = 6174, 85.5% of the total sample, see Table 1).
