Six of the SNPs presented in Table 4 also demonstrated moderate association with symptom count (rs17484734, rs12006002, rs2029519, rs4479194, rs7172677, rs11035102; all p<7.9 × 10−5) (Wang et al., 2012). The most significant association reported with the symptom count phenotype was with rs12903120 in C15orf53. This SNP was not associated with any of the phenotypes examined in this study (0.36≤p≤2.7 × 10−5). Since the symptom count phenotype is the total number of endorsed DSM-IV criteria, we might have expected more overlap between results with the individual criterion. However, there are several possible explanations for the observed differences. First, if our hypothesis is correct that different genetic factors may contribute to each criterion, then analyzing them separately would be a more powerful approach to identify the individual genetic effects. Second, there are some differences in the sample used in these two analyses as well as the analytic methods. For example, in the analyses reported herein, we employed a stricter inclusion criterion that only allowed regular drinkers. Previous analyses of alcohol symptom count utilized a more inclusive criterion that included all individuals reporting to have ever consumed alcohol.
