There is an intriguing convergence of genetic findings for nicotine and alcohol dependence with medical disorders. Smoking is the strongest risk factor for the development of lung cancer and chronic obstructive pulmonary disease (COPD). Large-scale genetic studies demonstrate that the same variants on chromosome 15 that are associated with smoking behavior are also the strongest genetic risk factors for lung cancer and COPD (Amos et al., 2008, 2010; Hung et al., 2008; Liu et al., 2008; Thorgeirsson et al., 2008; Broderick et al., 2009; Pillai et al., 2009; Shiraishi et al., 2009; Lips et al., 2010). The convergence of these genetic findings associated with smoking behavior and smoking related illnesses raises the question of whether this locus has a direct biologic effect on the risk of developing lung cancer and COPD, or if the increased genetic risk of lung cancer and COPD can be explained solely through the genetic influences on smoking behavior.
