Individuals were selected from the Minnesota Twin Family Study (MTFS) for moderate-depth whole genome sequencing. While we originally collected molecular genetic data from 7,845 individuals in the MCTFR (Iacono et al., 2014), we undertook whole genome sequencing for a subsample of 1,328 individuals due to prohibitive costs. Of these, 1,325 individuals from 602 families passed quality control checks and were available for association study. First, 1,038 individuals were sequenced as part of the NIDA Genes, Environment, and Development Initiative (GEDI; McGue et al., 2013). Next, 304 individuals were sequenced as part of a study of bipolar disorder (operating under the acronym BRIDGES and led by M. Boehnke at University of Michigan and R. Myers at HudsonAlpha) that is not yet completed and for which there are no currently available published sources. Sample selection within the MCTFR began by considering only individuals with self-reported European ancestry confirmed by genome-wide principal components, as described previously (Miller et al., 2012). The GEDI sample was selected in an attempt to maximize power to detect associations with measures of alcohol use and externalizing psychopathology (see
