It is now known that genetic factors influence variation in alcohol dependence, with heritability estimates reported to range 50–70% (Agrawal and Lynskey, 2008; Heath et al., 1997; Prescott and Kendler, 1995; Prescott and Kendler, 1999). Over the last two decades, several linkage scans have been undertaken to locate and identify the specific genes that contribute to alcohol dependence. Amongst these efforts are the Collaborative Study on Genetics of Alcoholism (COGA) (Begleiter et al., 1995; Reich et al., 1998) and the Irish Affected Sib-Pair Study of Alcohol Dependence (IASPSAD) (Prescott et al., 2006; Prescott et al., 2005), which have used linkage methods to identify loci on several chromosomes. These studies have focussed on patients with a family history of drinking problems.
