Addicted adult smokers smoke cigarettes to achieve levels of nicotine adequate to produce desired psychopharmacologic effects, such as fending off nicotine withdrawal (3); they adjust their smoking behavior to compensate for changes in the availability of nicotine or in the rate of elimination of nicotine from the body (4, 5). Thus, one would predict that those who metabolize nicotine more quickly will need to smoke more and will develop greater dependence. Indeed, in some (6–9) but not all (10–12) studies of adult smokers, genetically slower metabolizers of nicotine smoke fewer cigarettes per day. In addition, since the proportion of slower metabolizers decreases with increasing age of smoking, slower metabolizers appear to be more likely to quit than individuals with faster metabolism (9). Furthermore, because smokers with slow metabolism are under-represented among addicted smokers, some researchers have suggested that slower metabolizers are less likely to become addicted to nicotine (6–8). However, although it seems plausible that nicotine metabolism may affect smoking behaviors in adult smokers, the influence of nicotine metabolism during adolescence, when the development of nicotine dependence is most likely to occur, is less clear.
