Although environmental factors play an important role in nicotine dependence (ND),7 genetics is another important component, as ND has an average heritability of 0.56.7 Of the identified susceptibility genes for ND, the most investigated ones are members of the nicotinic acetylcholine receptor (nAChR) gene family, which encodes 12 subunits (i.e., α2–α7; β2–β4) that are widely expressed in many brain regions.8–10 Nicotine, a primary component of tobacco smoke, exerts its biological effects on these nAChRs, where it either stimulates them or inactivates them through desensitization.11 Here, CHRNA4 is linked to Norrie disease.