There is substantial evidence for genetic linkage to alcoholism phenotypes at the location of the main ADH gene cluster on chromosome 4 (Williams et al., 1999; Long et al., 1998; Prescott et al., 2006; Corbett et al., 2005), including linkage to maximum number of drinks ever consumed in a 24-hour period (max drinks) (Saccone et al., 2000), and alcohol consumption without dependence (Reich et al., 1998). Max drinks has also been linked to chromosomes 15 and 18 (Kuo et al., 2006). There is also evidence for linkage to maximum daily alcohol consumption on chromosome 9 at the location of ALDH1A1 (Bergen et al., 2003). In addition, variants in five alcohol-metabolizing genes, ADH4, ADH7, ADH1B, ADH1C and ALDH2, have been associated with alcohol-related phenotypes (Hurley et al., 2002; Li, 2000; Edenberg et al., 2006; Kuo et al., 2008; Luo et al., 2006; Luo et al., 2007; Birley et al., 2008; Matsuo et al., 2007; Ehlers et al., 2007).
