The low Level of Response (low LR) to alcohol is one of several early life genetically-influenced phenotypes that predict future heavy drinking and alcohol problems (King et al., 2013; Newlin & Renton, 2010; Quinn & Fromme, 2011; Schuckit, 2014). Whether measured as lower responses to oral alcohol challenges or as self-reports of more drinks required for effects (Schuckit et al., 2010), individuals with lower LRs require higher blood alcohol concentrations (BACs) for intoxication and/or to demonstrate physiological responses to alcohol. The latter include less alcohol-induced decreases in alpha activity in background cortical electroencephalograms, less prolonged P300 waves in evoked potentials, and less change in alcohol-sensitive hormones (Ehlers et al., 1999; Schuckit & Gold, 1988; Schuckit et al., 1988a, 1988b). Low LR has a heritability of .40–.60 (Heath et al., 1999; Luczak et al., 2002; Schuckit et al., 2001; Viken et al., 2003), and predicts higher future alcohol quantities and problems, even after controlling for earlier drinking (Chung & Martin 2009; Quinn & Fromme, 2011; Schuckit et al., 2007, 2008; Volavka et al., 1996).
