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Introduction: Most descriptions of tobacco withdrawal have not changed in >30 years despite new research. This meta-analysis tested whether abstinence leads to decreased positive affect (PA) because abstinence-induced symptom changes are a core feature of the tobacco withdrawal syndrome. In addition, we examined whether reduced PA was due to withdrawal (ie, temporary decrease in a "U-shaped" curve) or offset (ie, return to baseline) effect.Methods: Our main inclusion criterion was a prospective within-participant test of change in PA during abstinence conditions among people who smoke cigarettes daily who were not using a cessation medication. Our search of PubMed, PsycINFO, and personal libraries yielded a total of 32 tests with 2054 participants.Results: There was a medium effect size indicating an overall decrease in PA following abstinence from cigarettes (Cohen's d = -0.40, 95% CI = -0.30 to -0.49). There was large heterogeneity (I2 = 70.7%). Most (79%) of the 24 trials that conducted significance tests reported that reduction in PA was significant. Seven tests were adequately designed to detect a withdrawal versus offset effect. Over half (57%) displayed a U-shaped curve for abstinence-induced change in PA indicative of a withdrawal symptom rather than offset effect.Conclusions: Abstinence from cigarettes is associated with a decrease in PA. Whether low PA should be added to withdrawal measures and diagnostic criteria requires replication of the time-course of change in PA and tests of whether abstinence-induced changes in PA and negative affect occur independently.Implications: Though there was substantial heterogeneity among trials, our findings suggest that (1) abstinence from cigarettes decreases positive affect and (2) this decrease may represent a withdrawal effect (vs. an offset effect). However, it is unclear whether abstinence-induced losses in positive affect are independent from increased negative affect. [ABSTRACT FROM AUTHOR]

Background: Understanding study characteristics' influence on treatment efficacy could improve interpretation of trials' outcomes. We examined study characteristics as predictors of outcomes in clinical trials of medications for tobacco use.Methods: We obtained and analyzed data on 44 trials of nicotine gum, 37 trials of nicotine patch, 27 trials of varenicline, and 43 trials of bupropion from Cochrane reviews. We extracted and analyzed data for 15 study characteristics, odds ratios (ORs), and percent abstinent in control and medication conditions. We used general linear models to determine which study characteristics explained the variability among outcomes after controlling for medication characteristics.Results: Study characteristics accounted for 12% of the variance in odds ratios among patch trials, 16% among gum trials, 16% among varenicline trials, and 34% among bupropion trials above and beyond medication characteristics. Patch and gum trials with industry funding had larger odds ratios than those without. Among patch trials, this appeared to be due to less abstinence in industry-funded trials' control conditions. Bupropion trials published earlier had larger odds ratios, which appeared to be due to less abstinence in control conditions. The reason for study characteristics' influence on varenicline trials was unclear.Discussion: Study characteristics influenced the assessment of treatment efficacy above and beyond medication characteristics in smoking cessation trials. Our findings that study characteristics are associated with higher or lower efficacy does not suggest that the effect size under one versus another condition is the more valid outcome. Future studies are needed to determine which study characteristics reliably influence efficacy because this would help investigators and clinicians interpret trials.Implications: Study characteristics influenced the estimates of treatment efficacy but individual characteristics' influence on efficacy appeared to differ among different medications for smoking cessation. We encourage researchers to report study characteristics to improve interpretation of findings and systematic reviews, and to account for nontreatment-related variables to better estimate the efficacy of treatments. [ABSTRACT FROM AUTHOR]

Introduction: When animals undergo nicotine deprivation, rewards become less rewarding (ie, anhedonia occurs). We searched for tests of whether anhedonia occurs in abstinent smokers.Methods: The major inclusion criterion was a within-participants comparison of behavioral measures of reward sensitivity or self-reported anhedonia during smoking versus during abstinence among daily smokers. A computerized search of PubMed, PsychInfo, and Cochrane databases and other methods located 13 studies. All but one were laboratory studies.Results: The number of studies and participants were small and the results mixed. In terms of anticipatory anhedonia (ie, wanting a reward), abstinence appeared to decrease willingness to work for immediately available rewards, but did not appear to influence how much adding rewards to a task increased responding. Abstinence also appeared to produce small increases in self-reported anticipatory anhedonia. In terms of consummatory anhedonia (ie, liking a reward), self-report measures found anhedonia decreased pleasure from rewards in some but not all tests. In terms of learning (ie, learning to choose a more frequent reward), abstinence did not reliably decrease allocating responding to high versus low frequency reward options.Conclusions: Although results were mixed, abstinence appears to increase anticipatory anhedonia. It is unclear if abstinence increases consummatory or reward learning-based anhedonia. Further studies of anhedonia in clinical settings are needed (1) to estimate the reliability and clinical significance of anhedonia as a symptom of tobacco withdrawal, (2) to assess if effects represent withdrawal versus offset processes, and (3) to assess if anhedonia interferes with the ability to stop smoking.Implications: Anticipatory anhedonia appears to be a symptom of tobacco withdrawal and should be added to tobacco withdrawal checklists and diagnostic criteria. Further study of consummatory and learning-based anhedonia is warranted. [ABSTRACT FROM AUTHOR]