Contrary to our hypothesis, slower metabolizers actually smoked more cigarettes per day and had higher addiction scores than did faster metabolizers. The finding of increased cigarettes per day among slower metabolizers is the opposite of findings in some other studies of adolescent smokers (13, 19) and most studies of adult smokers (28, 33, 34). Specifically, in other studies, faster rates of nicotine clearance are generally associated with greater numbers of cigarettes smoked per day (13, 19, 35). Our finding of an association between slower metabolism using the NMR and higher addiction scores is also novel. To the best of our knowledge, no studies of smokers have reported significant associations between the NMR and addiction scores. It is worth noting that most of the participants had relatively low scores on the mFTQ. However, evidence suggests that similar measures are valid down to extremely low levels of dependence, as demonstrated by Shiffman and colleagues (36, 37), who found meaningful and measurable variations in dependence even among very light and intermittent smokers.
