In parallel with the studies of smoking, large scale genetic studies of lung cancer and COPD have been undertaken, and the same variants on chromosome 15 are associated with these smoking related diseases [21-24]. This represents an exciting convergence of genetic findings for nicotine dependence, smoking quantity, lung cancer, and COPD risk. The identification of this common genetic region that is associated with smoking behavior and smoking related illnesses raises the question of whether this locus has a direct effect on lung cancer and COPD vulnerability, or whether this increased genetic risk of lung cancer and COPD can be explained solely through the genetic influence on heavy smoking. A direct effect of this locus on lung cancer and COPD may represent pleiotropy where a single genetic region influences multiple diseases.
