62 Tobacco Control 2001;10:62–64 Tob Control: first published as 10.1136/tc.10.1.62 on 1 March 2001. Downloaded from COMMENTARY Why does smoking so often produce dependence? A somewhat diVerent view John R Hughes Abstract These explanations often give little emphasis The usual explanation for why smoking to the possibility that nicotine induces depend- produces dependence focuses on the ence because it produces beneficial eVects that eVects of nicotine on dopamine and other can help smokers cope with their environ- neurobiological explanations. This review ment.89 By beneficial eVects, I mean positive oVers four somewhat diVerent explana- eVects that are not due to relief of withdrawal tions: (1) nicotine can oVer several but rather are eVects above and beyond a “nor- psychopharmacological benefits at the age mal” baseline functioning.10 when such benefits are especially needed; Whether nicotine via smoking causes true (2) cigarettes provide for a rapid, beneficial eVects is, to many, debatable.891112 frequent, reliable and easy-to-obtain My belief (and that of others before me89) that reward; (3) nicotine is not intoxicating, nicotine can cause true beneficial eVects is allowing chronic intake; and (4) the long based on three sets of data. First, nicotine often duration of the nicotine withdrawal causes improvements in animals with no syndrome eVectively undermines cessa- history of nicotine exposure, in never smokers, tion. This article reviews the evidence for and in non-deprived smokers.8911 Second, the above views and the tobacco control most other drugs of dependence produce ben- activities these views suggest. eficial eVects—for example, cocaine produces (Tobacco Control 2001;10:62–64) stimulation and alcohol produces relaxation http://tobaccocontrol.bmj.com/ Keywords: nicotine; substance use disorder; substance and increased confidence. Third, the two other withdrawal; tobacco use disorder major explanations for nicotine dependence (euphoria and withdrawal relief) have Many of us are asked by fellow scientists, problems explaining the persistence of administrators, clinicians, acquaintances, and smoking. Euphoria is endorsed only 10% of tobacco lawyers why we think cigarette the time while smoking13 plus very few smokers smoking produces dependence. The usual report euphoria as a reason for smoking.14 response often emphasises brain changes, Withdrawal is often reported by adolescents7; genetics and other neurobiological explana- however, 77% of adolescents deny ever using tions as described in the 1988 surgeon cigarettes to avoid withdrawal symptoms.15 I general’s report.1 The present article proposes am not denying euphoria or withdrawal occur; four other factors that I and others believe are however, I believe they cannot adequately on September 24, 2021 by guest. Protected copyright. as important, to understanding nicotine explain the persistence of smoking. dependence (in this paper “dependence” refers Nicotine’s beneficial eVects are probably to the Diagnostic and statistical manual of mental especially potent in the transition from experi- disorders, fourth edition (DSM-IV) definition2). mental to regular smoking. Nicotine can My views are not new; however, I believe they produce several diverse eVects—that is, it can are much under appreciated both by tobacco reduce aggression, improve focus on cognitive control advocates and by biological scientists. tasks, increase vigilance, decrease weight gain, Plus, I believe they suggest concrete changes in and improve mood.16 These beneficial eVects Department of our tobacco control activities. are probably especially appealing to teenagers. Psychiatry, University Consider the issues most teenagers are dealing of Vermont, with. Many are trying to control their Burlington, Vermont, USA Nicotine, the “renaissance drug” aggression, to focus attention for long periods J R Hughes A common explanation of why nicotine and of time, to control their weight or to control other drugs can be dependence producing their mood.6 Typically, they have trouble mas- Correspondence to: John R Hughes MD, focuses on how drugs increase dopamine and tering these skills. When adolescents Department of Psychiatry, act on “reward centres” of the brain.1 3–5 Some- experiment with cigarettes, they may find that University of Vermont, 38 Fletcher Place, Burlington, times these explanations emphasise positive nicotine can help with some of these problems, VT 05401–1419, USA reinforcement (that is, pleasurable eVects often plus it is likely to be a more reliable solution john.hughes.uvm.edu termed euphoria) as the main cause of than their own fledgling skills. Although we 1 3–5 Received 26 May 2000 and dependence. Other times they emphasise have no direct tests of beneficial eVects of nico- in revised form 1 October 2000. Accepted 12 negative reinforcement—that is, smokers use tine in adolescents, it does seem likely that October 2000 cigarettes mostly to avoid withdrawal.367 many adolescents come to use cigarettes as a www.tobaccocontrol.com Why smoking induces dependence 63 Tob Control: first published as 10.1136/tc.10.1.62 on 1 March 2001. Downloaded from multipurpose pharmacological coping strategy. Duration of nicotine withdrawal Whether this use of cigarettes for beneficial To many lay persons, a severe withdrawal syn- eVects persists and maintains smoking into drome which produces physical changes is a adulthood or whether the motive for smoking central characteristic of a drug dependence. changes to withdrawal relief is still unclear. Although nicotine withdrawal can be severe in some smokers, in most smokers it is not.23 24 I Rapid, frequent, reliable and believe the reason nicotine withdrawal is easy-to-attain eVects from nicotine via important is not its severity but rather its dura- cigarettes tion.24 Multiple studies have found that the Many lay persons believe the magnitude of a average duration of withdrawal is about three reward is the most important determinant of weeks and that a substantial proportion of its eYcacy. In reality, the rapidity, frequency, smokers (> 40%) have withdrawal symptoms reliability, and ease of attainment of the reward that last longer than three weeks.24 I believe are as important, if not more important.17 I, that it is this chronic, low grade discomfort that and others before me,18 believe nicotine via undermines smoking cessation. For example, cigarette smoking is so dependence producing chronic hunger undermines many attempts to because it maximises all four of these eVects. lose weight, even though hunger on any one First, nicotine via cigarettes is absorbed via day may not be severe. In addition, I believe the lung, directly into the arterial system, with- that many smokers who are still irritable, hun- out dilution of the venous system, and reaches gry, and anxious after three weeks believe this the brain within 10 seconds.1 This is faster than is how they will be for the rest of their life with- intravenous use. I know of few rewards that out cigarettes. Faced with this possibility, it is occur quicker. Second, if one smokes 20 understandable why many smokers would cigarettes a day and takes 10 puVs per relapse. Earlier studies that focused on the cigarette, this means 200 rewards per day. I severity of withdrawal did not find withdrawal know of no other reward that occurs so undermined cessation.25 However, more frequently in daily life. Third, unlike sophisticated recent studies have found that purchasing illicit drugs on the street in which abstinent smokers whose withdrawal abates the purity varies from sale to sale, with slowly are much more likely to relapse than cigarettes, one gets exactly the same dose with those whose withdrawal abates rapidly.26 Thus, each purchase. Fourth, because of ubiquitous the evidence supports the notion that the dura- marketing and underage sales, purchasing of tion of withdrawal is important. cigarettes requires significantly less eVort than purchasing illicit drugs or alcohol. Perhaps the Implications for tobacco control best evidence for this view is that when These four particular features of nicotine http://tobaccocontrol.bmj.com/ nicotine is delivered via medications in which dependence suggests possible changes in the delivery is slow, infrequent and costly (for tobacco control activities. The major example, transdermal nicotine), then the implication of the first view—nicotine has sev- dependence potential of nicotine is low.34 eral beneficial eVects—is that prevention programmes perhaps should stop denying this. Nicotine is not intoxicating Most smokers believe nicotine has beneficial A common criticism of defining smoking as a eVects.13 Denying such eVects undermines the nicotine dependence is that, unlike other drug credibility of prevention programmes. We do dependencies, smoking does not cause not try to deny that cocaine stimulates or that intoxication and the related extreme behav- alcohol is relaxing in prevention programmes, iours (for example, crime or violence).19 I so why deny beneficial eVects for nicotine? believe the lack of intoxication from nicotine Admitting nicotine has beneficial eVects can be on September 24, 2021 by guest. Protected copyright. makes it more addicting, not less addicting. integrated into prevention programmes by This lack of intoxication allows the smoker to pointing out that smoking is sometimes a ingest large amounts of a drug without causing “pharmacological crutch”. social problems, increasing the probability of The major implication of the second view— experiencing beneficial eVects