Eligible studies had to meet the following criteria: they (i) were published in peer-reviewed journals and contained original data; (ii) presented sufficient data to calculate the odds ratio (OR) with confidence interval (CI) and P value; (iii) were association studies investigating the specific SNP discussed here (rs671); (iv) described or referenced appropriate genotyping methods or protocols; (v) investigated alcohol or drug dependence (or abuse) diagnosed by valid and published criteria. For the studies investigating alcohol-induced liver disease, cirrhosis, or chronic pancreatitis, the cases were considered as alcoholics with the diseases attributable to alcoholism. Cirrhosis was diagnosed by histological, clinical, radiological, and (or) endoscopic findings; (vi) had no description of other major psychiatric disorders for the patients except anxiety or depressive disorder (patients of AD are often comorbid with anxiety disorder or depressive disorder, or the status was unknown in some studies); and (vii) used unrelated individuals in case-control studies and healthy individuals (or random population) as controls. Authors were contacted in cases where we determined it would be useful to have additional information regarding their studies.
