Extensive work has explored the relationship between OPRM1 A118G and various substance abuse disorders, specifically alcohol abuse disorders (Bergen et al., 1997; Gelernter, Kranzler, & Cubells, 1999; Town et al., 1999; Schinka et al., 2002; Crowley et al., 2003; Luo, Kranzler, Zhao, & Gelernter, 2003; Kim et al., 2004; Loh, Fann, Chang, Chang, & Cheng, 2004; Nishizawa et al., 2006; Szeto, Tang, Lee, & Stadlin, 2001; Türkan et al., 2019). This has profound treatment implications, since naltrexone, an opioid receptor antagonist, decreases relapse in alcoholic individuals (Jonas et al., 2014) and is one of the few adjunctive therapies approved for the treatment of subjects with AUDs. Analysis of G-allele carriers diagnosed with an AUD responded more strongly to naltrexone, with lower rates of relapse and a longer time to return to heavy drinking (Oslin et al., 2003). However, a more recent study failed to observe the same effect (Oslin et al., 2015; Sloan et al., 2018), but reported that G-allele carriers consume more drinks per day, on average. This study’s findings may differ from previous meta-analyses because the authors omitted
