From each publication, full text of the original papers were downloaded and manually curated to extracted meta-data, such as publication information ('PubMed ID', 'First Author', 'Title', 'Year' and 'Study Method'), sample information ('Study Design', 'Sample Size,' 'Age', 'Gender Ratio' and 'Ethnic Group'), drug information ('Addictive Drug' and 'Behavior Description'), genotype information ('Gene ID', 'SNP/Marker ID', 'Primary Significance Report', 'Detailed Genotypes in Case and Control' and 'HWE P-value') and curation information ('Curator' and 'Date') (Additional file 1). A full list for the curated information is online available at http://karg.cbi.pku.edu.cn/karg2/.
