Effects of abstinence from tobacco: etiology, animal models, epidemiology, and significance: a subjective review.

This article updates a 1990 review of the effects of tobacco abstinence by reviewing (a) the etiology, (b) animal models, (c) the epidemiology, and (d) the clinical significance of tobacco abstinence effects. The author searched several databases to locate more than 3,500 citations on tobacco abstinence effects between 1990 and 2004. For brevity, the review does not evaluate these effects in regard to craving, hunger, or performance. Data collection and study conclusions were based on the author's subjective judgment. The most validated etiological model suggests that withdrawal is related to decreased dopaminergic activity, but how this relates to nicotine receptor changes is unclear. The two most validated animal models describe increases in intracranial self-stimulation thresholds or observable physical signs. Significant withdrawal symptoms occur in at least half of smokers when they try to quit. Withdrawal appears to produce clinically significant distress and impairment. Increases in depression after abstinence, but not other symptoms, prospectively predict relapse. In conclusion, the proposed neurobiological mechanisms by which withdrawal occurs leave several unanswered questions. Although animal models have been developed, how well they mimic withdrawal in humans is unclear. Tobacco withdrawal is common and can be distressing. Withdrawal-induced depression appears to undermine the smoker's ability to remain abstinent.