Progesterone increases nicotine withdrawal and anxiety in male but not female smokers during brief abstinence

This double-blind, randomized crossover study examined the effects of progesterone versus placebo on symptoms of nicotine use disorder in 66 non-treatment-seeking male and female smokers over a four-day abstinence period. As part of the study, expired CO levels were measured using the Vitalograph BreathCO carbon monoxide monitor.