reported that the relationship between stressful life events and depression was highly robust, but was not moderated by 5-HTTLPR genotype. However, the role of nicotine in these studies is unknown. The effect of genotype on smoking behavior and/or withdrawal is likely more complex and may require more in-depth investigation than basic phenotypes typically allow (i.e., smoker versus non-smoker or quitter versus non-quitter). There may be more subtle neurobiological pathways that are influenced by genotype which in turn are related to withdrawal symptoms or inability to quit smoking. It is also possible that l/l smokers are vulnerable for different reasons than s-carrier smokers, as there are many variables associated with smoking and withdrawal behavior (affect, cognitive functioning, etc.).
