It has been shown that allelic variation in the α5 nicotinic acetylcholine receptor (nAChR) gene <i>CHRNA5</i> is associated with higher risk of tobacco dependence.
Indeed, genetic variation in the CHRNA5-CHRNA3-CHRNB4 gene cluster, encoding the α5, α3, and β4 nAChR subunits, respectively, has been shown to increase vulnerability to tobacco dependence and smoking-associated diseases including lung cancer.