Threshold dose for behavioral discrimination of cigarette nicotine content in menthol vs. non-menthol smokers

Rationale The lowest threshold content (or "dose") of nicotine discriminated in cigarettes may differ due to menthol preference. Objectives Menthol and non-menthol Spectrum research cigarettes differing in nicotine content were used to determine discrimination thresholds. Methods Dependent smokers preferring menthol (n = 40) or non-menthol (n = 21) brands were tested on ability to discriminate cigarettes (matched for their menthol preference) with nicotine contents of 16-17, 11-12, 5, 2, and 1 mg/g, one per session, from an "ultra-low" cigarette with 0.4 mg/g. Controlled exposure to each cigarette was four puffs/trial, and the number of sessions was determined by the lowest nicotine content they could discriminate on > 80% of trials (i.e., = 5 of 6). We also assessed subjective perceptions and behavioral choice between cigarettes to relate them to discrimination responses. Results Controlling for Fagerstrom Test of Nicotine Dependence score, discrimination thresholds were more likely to be at higher nicotine content cigarettes for menthol vs. nonmenthol smokers (p <.005), with medians of 16 vs. 11 mg/g, respectively. Compared to the ultra-low, threshold and subthreshold (next lowest) cigarettes differed on most perceptions and puff choice, but menthol preference did not alter these associations. Notably, threshold cigarettes did, but subthreshold did not, increase choice over the ultra-low. Conclusions Threshold for discriminating nicotine via smoking may be generally higher for menthol vs. nonmenthol smokers. More research is needed to identify why menthol smoking is related to higher nicotine thresholds and to verify that cigarettes unable to be discriminated do not support reinforcement.