By meta-analyzing the 6 race-by-study strata (Table 2), the differences between nicotine and the other substances became even more apparent. In contrast to the nicotine dependence meta-analysis p-value (8.6×10−5), the meta-analysis p-values for alcohol, cocaine, and marijuana are 0.34, 0.24, and 0.97, respectively, again demonstrating no statistical evidence for association between variation in rs13273442 and dependence on these substances independent of the association with nicotine dependence.
