CHRNA4 and nicotine dependence: CHRNA3 rs578776 polymorphism was reported to be associated with change in nAChR functioning (Wang et al., 2009; Wen et al., 2016), and with nicotine dependence levels (Saccone et al., 2009a), while such associations could not be shown by some other studies (Hubacek et al., 2014; Tyndale et al., 2015).