To address whether a variant increasing the risk for tobacco smoking and nicotine dependence also increases risks for alcohol and cannabis abuse or dependence, we tested the association with the symptoms of alcohol and cannabis abuse/dependence phenotypes in the combined sample. Table V summarizes the results of these analyses. Two markers (rs16969968 and rs1051730) were significantly associated with SymAlcAD when the effects of FTND scores were taken into consideration by using them as a covariate (P = 0.0072 and 0.0057, respectively) (Table V). Both markers remained significant after correction for multiple testing. However, the risk alleles for high SymAlcAD were the opposite alleles to what we found associated with FTND. Interestingly, the study of Wang et al. [2008] found the same pattern of results. No association was found with SymCanAD in the combined sample.
