Threshold for the pleasurable effects of nicotine are lower than its reinforcing effects during self-administration

This double-blind, crossover study examined the similarity between thresholds for the subjective and physiological effects of nicotine in 34 young adult daily smokers given repeated opportunities to choose blinded doses of nicotine versus placebo. As part of the study, overnight smoking abstinence was confirmed by measuring expired-breath carbon monoxide using the Vitalograph BreathCO device.