Studies identified through these methods were then selected based on the following criteria: (a) inclusion of individuals diagnosed with alcohol dependence according to Diagnostic and Statistical Manual 3rd Edition, Revised (DSM-III-R; (American Psychiatric Association, 1987) or DSM-IV (American Psychiatric Association, 1994) criteria; (b) inclusion of a control group; and (c) results of genotyping did not violate Hardy-Weinberg equilibrium (HWE). Additionally, studies were included only if sufficient information to determine the number of participants with each genotype in both groups could be extracted from data presented in the article, or if such data was provided by study authors upon request. Data were abstracted from the articles by one of the authors (RKM) and independently checked for accuracy.
