Given the potential functional relevance of rs1799971 to mu-opioid receptor activity, numerous investigations have examined the association of rs1799971 with alcohol-related behaviors and alcohol use and dependence. Individual studies have reported associations of rs1799971 with phenotypes such as alcohol cue-reactivity (Ray et al., 2014b; Courtney et al., 2015; Bach et al., 2015) and subjective response and sensitivity to alcohol’s effects (Ray et al., 2013, 2014a; for a review, see Ray et al., 2012). More broadly, rs1799971 has been associated with measures of alcohol use, such as drinking levels (e.g., Pfeifer et al., 2015), alcohol self-administration concentrations (Hendershot et al., 2014), and dependence rates (van der Zwaluw et al., 2007), all of which correlate highly with subjective response to alcohol. However, findings are mixed with regard to the presence or direction of effect. Meta-analyses have been conducted to identify the extent of influence conferred by rs1799971 (Arias et al., 2006; Chen et al., 2012; Schwantes-An et al., 2016). Most recently, the largest of these investigations assessed both general substance dependence (as defined by a DSM-IV lifetime dependence diagnosis for any of
