Most large-scale genetic association studies have tested for genetic effects on lifetime clinical diagnoses of substance use and psychiatric disorders. For example, there are large-scale efforts underway to identify genes involved in alcohol dependence (Bierut, Agrawal et al. 2009; Edenberg, Koller et al. 2010), schizophrenia (Ripke, Sanders et al. 2011; Lee, DeCandia et al. 2012), major depression (Consortium 2012; Wray, Pergadia et al. 2012), bipolar disorder (Chen, Jiang et al. 2011), autism (Chahrour, Yu et al. 2012; Sanders, Murtha et al. 2012), and attention-deficit hyperactivity disorder (Elia, Glessner et al. 2012; Stergiakouli, Hamshere et al. 2012; Williams, Franke et al. 2012). There has also been interest in expanding gene identification efforts to include phenotypes additional to clinical diagnoses. This has involved studying: behavioral components related to psychiatric and substance use disorders (e.g., drinking patterns) (Dick, Plunkett et al. 2006); subtypes that may have more homogeneous etiologies (e.g., early onset alcohol dependence) (Edenberg, Xuei et al. 2007); and broader phenotypes that may jointly reflect a shared etiology (e.g., by studying general externalizing or internalizing disorders) (Hettema, An et al. 2006; Dick,
