Gene identification efforts for substance use and psychiatric outcomes have come a long way over the past decade. For many years gene identification efforts were disappointing, with a history of linkage studies yielding modest lod scores (Agrawal et al., 2008, Dick et al., 2006a, Dick et al., 2004, Foroud et al., 2000, Kim et al., 2005), candidate genes with poor replication records (Allen et al., 2008, Chanock et al., 2007, Lohmueller et al., 2003, Risch et al., 2009), and early genome-wide association studies that produced null findings (The Wellcome Trust Case Control, 2007). The study of substance use disorders provided rare exceptions, whereby genes encoding nicotinic receptor subunits (Saccone et al., 2007, Hancock et al., 2015, Thorgeirsson et al., 2008), as well as alcohol metabolizing enzyme genes (Gelertner et al., 2014, Bierut et al., 2012), were consistently and robustly associated with nicotine and alcohol dependence, respectively. However, even the considerable body of “failed” studies were quite informative. The expectation that individual genetic variants would be associated with psychiatric disorders at a magnitude that would be small but detectable with hundreds,
