not among carriers of dopaminergic gene variants - possibly, suggesting that either: the effect of nicotinic receptor genes is larger than that of dopaminergic genes or that the effect of dopaminergic genes does not vary as a function of environmental context. Under these assumptions, we might hypothesize that cigarette use initiation may be more heavily influenced by genes predisposing individuals to addictive behaviors via effects on neurotransmitter pathways, such as genetic variants that contribute to novelty seeking (109), while daily smoking, the number of cigarettes smoked per day, and nicotine dependence may have more to do with genes that contribute to nicotine response, such as genes influencing nicotine metabolism (110–112).
