The HuGE database was used to survey articles on the ten candidate genes that had the most publications (listed in Table 2). The most well established loci based on expert opinion of the literature for each of the top ten candidate genes was searched in the genome browser to test whether candidate loci that had been highly reported in candidate gene studies replicated in the SAGE dataset. Since allele A9 for SLC6A3 is a VNTR, we examined the two SNPs rs27072 and rs27048 as proxies because they have been found to be associated with similar withdrawal symptoms and are roughly in the same region of the gene as the VNTR (Le Strat et al., 2008). As the originators of the SAGE dataset, we were also able to compare the odds ratios and p values within the original three datasets (COGA, FSCD and COGEND) to verify whether there was any heterogeneity across the three contributing studies.
