Complex behavioral outcomes such as alcohol use are quite distal from the level of genetic function. Thus, studying the role of intermediate phenotypes may help to unpack the pathways through which genetic risk unfolds to influence psychiatric and behavioral outcomes (Gottesman & Gould, 2003; Lenzenweger, 2013). Sensation seeking, or a tendency to seek out novel sensations and experiences (Zuckerman, 1984), is an especially compelling intermediate phenotype in molecular genetic studies of alcohol phenotypes. First, sensation seeking is a personality trait that co-segregates with alcohol use disorder (AUD). For example, individuals with a family history of AUD tend to report higher levels of sensation seeking than those without a family history of AUD (Grucza et al., 2006; Sher et al., 1991). Second, sensation seeking is moderately heritable, with an estimated heritability of 40%-80% (Harden et al., 2012). In addition, twin studies showed substantial overlap in the genetic etiology between sensation seeking and alcohol use outcomes (Mustanski et al., 2003; Slutske et al., 2002). Finally, high sensation seeking is robustly associated with alcohol use among adolescents and adults (Hittner & Swickert, 2006),
