For these reasons, genome-wide association studies (GWAS) has gained favor. GWAS theoretically combines the advantages of linkage mapping (a systematic genome-wide scan that has the capability of identifying novel genetic variants) and the advantages of association (higher resolution that provides more power to detect genes of subtle effect). Currently, there is only 1 published GWAS for alcohol dependence.55 Treutlein and colleagues55 found 2 genome-wide significant results in closely linked intergenic single nucleotide polymorphisms (SNPs), located on chromosome region 2q35, and 9 SNPs located in genes (CDH13 and ADH1C), all of which have previously been implicated in the alcohol dependence literature. This study is the first published GWAS to identify a genome-wide significant association in alcohol dependence. In addition to this study, many GWAS are currently underway for alcohol-related phenotypes including efforts from large gene identification projects, the COGA, the Irish Affected Sib-Pair Substance and Alcohol Dependence (IASPSAD), and the Study of Addiction: Genetics and Environment (SAGE), with results expected imminently. Although GWAS provides several advantages, including the ability to more precisely localize associated variants, it also provides many challenges including
