INDIVIDUAL-DIFFERENCES IN NICOTINE SENSITIVITY

It is suggested that individual differences in sensitivity to nicotine may help account for a number of anomalous findings uncovered in research on nicotine regulation. However, an examination of the literature reveals very little pertinent evidence. To demonstrate the existence of such differences, 124 male and female subjects were screened for responsiveness to nicotine by smoking a standard cigarette while their heart rates were continuously monitored for 5 minutes before, during, and after smoking. Puff analyses were also conducted to determine the amount of nicotine subjects obtained from cigarettes. Based on increases in heart rate of more than 10 or less than 8 beats per minute from baseline to smoking periods, subjects were categorized as responsive or nonresponsive. To assess stability of responsiveness over time, 20 responsive and 20 nonresponsive subjects were called back for a second session 1 week to 4 months later. At the second session, heart rates were again monitored before, during, and after smoking a standard cigarette. The data indicate that subjects maintained their relative degree of sensitivity to nicotine over time. The results are discussed in terms of Solomon''s opponent process model and it is suggested that not all smokers are addicted to nicotine.