The GWAS sample is drawn from participants in one of three longitudinal studies undertaken under the auspices of the MCTFR: 1) the Minnesota Twin Family Study (MTFS) (Iacono, Carlson, Taylor, Elkins, & McGue, 1999); 2) the Sibling Interaction and Behavior Study (SIBS) (McGue et al., 2007), and 3) the Enrichment Study (ES) (Keyes et al., 2009). These studies utilized similar assessment protocols and a common sampling unit, a 4-member family consisting of a pair of siblings and their rearing parents. The offspring in all three samples were initially assessed in adolescence and followed into at least early adulthood. In total, 9827 individuals (5001 offspring and 4826 parents) have completed a MCTFR intake assessment. Table 1 provides a descriptive overview of the MCTFR samples.
