Thus, although the ADH1B and ALDH2 genotypes are risk factors for both alcohol dependence [6–10] and esophageal cancer [15, 25, 37], it is unlikely that the potential selection bias of the controls, i.e., esophageal-cancer-free and imperfect exclusion of alcohol dependence, significantly affected the present results due to their low prevalence. Here, ALDH2 is linked to alcohol dependence.