title: The effects of nicotine stimulus and response expectancies on male and female smokers' responses to nicotine-free electronic cigarettes.
abstract: BACKGROUND
  Electronic cigarettes (e-cigarettes) have been reported to reduce tobacco craving and withdrawal; however, the mechanisms underlying these effects have not been elucidated.
  
  
  METHODS
  This study examined the contributions of nicotine stimulus and response expectancies to responses to nicotine-free e-cigarettes in 21 e-cigarette naïve smokers (12 male). Participants completed two randomized experimental sessions in which they administered a nicotine-free e-cigarette. During one session they were informed that the e-cigarette contained nicotine and during the other session they were informed that the e-cigarette was nicotine-free. Participants completed subjective assessments before and immediately after sampling ten puffs from the e-cigarette and were then invited to earn additional puffs using a computerized progressive ratio task. Prior to their enrolment in the study, participants provided an estimate of the relative importance of the nicotine content of e-cigarettes for craving relief.
  
  
  RESULTS
  Instructions that the e-cigarette contained nicotine were found to reduce both intention to smoke (p=0.017) and withdrawal-related (p=0.018) craving, regardless of a-priori reported beliefs regarding the relative importance of nicotine. Nicotine content instructions were also found to be associated with a shorter latency to self-administration (p=0.005); however, a Sex×Instructions×Response Expectancy interaction (p=0.008) revealed that this effect was specific to women who had strong a-priori nicotine content craving relief expectations. Neither nicotine content instructions nor response expectancies impacted the number of puffs self-administered.
  
  
  CONCLUSIONS
  Findings suggest that nicotine content expectations contribute to smokers' responses to e-cigarettes, and that a-priori beliefs about nicotine effects may be especially important in women.
authors.affiliation: Department of Psychology and Neuroscience, Dalhousie University, Canada.
authors.forename: Sebastian R
authors.initials: SR
authors.lastname: Copp
authors.affiliation: Department of Psychology and Neuroscience, Dalhousie University, Canada.
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Collins
authors.affiliation: School of Psychological Sciences, Tel Aviv University, Israel.
authors.forename: Reuven
authors.initials: R
authors.lastname: Dar
authors.affiliation: Department of Psychology and Neuroscience, Dalhousie University, Canada. Electronic address: sean.barrett@dal.ca.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Barrett
mesh_terms: D000328:Adult; D066249:Craving; D066300:Electronic Nicotine Delivery Systems / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009538:Nicotine / Q000008:administration & dosage* / Q000009:adverse effects; D018722:Nicotinic Agonists / Q000008:administration & dosage* / Q000009:adverse effects; D015990:Placebo Effect; D012646:Self Administration; D012737:Sex Factors; D012907:Smoking / Q000523:psychology*; D013375:Substance Withdrawal Syndrome / Q000209:etiology; D055815:Young Adult
chemical_list: D018722:Nicotinic Agonists; D009538:Nicotine
keywords: Craving; Electronic cigarettes; Expectancy; Nicotine; Self-administration