Fourth, as noted above, the list of genes that distinguish successful from unsuccessful quitters should be considered as a list of nominees, in light of the modest power available for this comparison and the likely inclusion of false-positive results on this list. In spite of this caution, however, we do find that this list of these genes overlaps with the genes that distinguish nicotine-dependent from control individuals. We also note that these positional cloning results identify genes whose products can substantially impact animal models for relapse. We identify corticotrophin releasing hormone (CRH), for example. Stressors of several sorts elevate CRH and lead to dramatically elevated relapse in animal models [50]. We also identify a gene cluster that contains two melanocortin G protein coupled receptors. We have never consistently identified CRH or melanocortin receptor genes in our studies comparing addicts to controls. These CRH and melanocortin receptor genes are thus candidates to contribute to the genetic influences on quitting success that may be independent of the genetic influences on nicotine dependence. Fifth, there are modest to moderate differences in the gender
