Participants were drawn from two studies at the Minnesota Center for Twin and Family Research (MCTFR; Iacono et al., 2006): the Minnesota Twin Family Study (MTFS; Iacono et al., 1999) comprising twins and their families, and the Sibling Interaction and Behavior Study (SIBS) (McGue et al., 2007), which includes adopted and biological sibling pairs and their families. Both studies are population based and longitudinal, with an initial assessment when twins and siblings are in adolescence, and follow-up assessments every three or four years thereafter. For this study, both offspring (twins and siblings) and their parents were included in analyses. Parent data were collected at their family’s first visit to the MCTFR, while for non-parental participants, data were taken from assessments conducted between ages 16.5 and 21. Only white MCTFR participants were included in the sample, as determined by clustering in 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
