CHRNA5 and lung cancer: The variants in CHRNA5-A3-B4 give rise to the over expression of the nAChRs in in the key regions of brain which may make individuals sensitive to nicotine, which includes the pharmacological effects of nicotine along with higher activation of the medial habenula and reduced activation of dopaminergic neurons after acute nicotine administration[35,36], and thus lead to smoking more cigarettes over a long period, a well-established etiological factor for lung cancer.