The sequenced sample comprises 363 subjects from the Virginia Twin Study on Adolescent Behavioral Development (VTSABD)(Meyer et al., 1996) and 443 subjects from the Minnesota Twin Family Study (MTFS)(Iacono et al., 1999, Miller et al., 2012). Both of these studies are twin samples, however, based on random selection, only one subject per twin pair was sequenced. Table 1 provides summary descriptives data for each of the samples. The sequenced MTFS samples had a higher composition of males and monozygotic twins when compared to the VTSABD. All subjects were of European ancestry. Blood samples were collected from which DNA was extracted. Ethical committees in the USA approved all procedures, and all subjects provided written informed consent.
