Smoking cessation

Methods

Major reviews of the scientific literature on smoking cessation include:

Systematic reviews of the Cochrane Tobacco Addiction Group of the Cochrane Collaboration. As of 2016, this independent, international, not-for-profit organization has published over 91 systematic reviews "on interventions to prevent and treat tobacco addiction" which will be referred to as "Cochrane reviews" in this article.

Clinical Practice Guideline: Treating Tobacco Use and Dependence: 2008 Update of the United States Department of Health and Human Services, which will be referred to as the "2008 Guideline." The Guideline was originally published in 1996 and revised in 2000. For the 2008 Guideline, experts screened over 8700 research articles published between 1975 and 2007. More than 300 studies were used in meta-analyses of relevant treatments; an additional 600 reports were not included in meta-analyses, but helped formulate the recommendations. Limitations of the 2008 Guideline include not evaluating studies of "cold turkey" methods ("unaided quit attempts") and its focus on studies that followed up subjects only to about 6 months after the "quit date" in order to capture the greatest number of studies for analyses. (Most relapse occurs early in a quit attempt, though relapse can occur later - even years later

Unassisted

It is common for ex-smokers to have made a number of attempts (often using different approaches on each occasion) to stop smoking before achieving long-term abstinence. A recent study estimated that ex-smokers make between 6 and 30 attempts before successfully quitting. Identifying which approach or technique is eventually most successful is difficult; it has been estimated, for example, that only about 4% to 7% of people are able to quit smoking on any given attempt without medicines or other help. A recent review of unassisted quit attempts in 9 countries found that the majority of quit attempts are still unassisted, though the trend seems to be shifting. In the U.S., for example, the rate of unassisted quitting fell from 91.8% in 1986 to 52.1% during 2006 to 2009. The most frequent unassisted methods were "cold turkey", a term that has been used to mean either unassisted quitting or abrupt quitting and "gradually decreased number" of cigarettes, or "cigarette reduction".

Cold turkey

"Cold turkey" is a colloquial term indicating abrupt withdrawal from an addictive drug, and in this context indicates sudden and complete cessation of all nicotine use. In three studies, it was the quitting method cited by 76%, 85%, or 88% of long-term successful quitters. In a large British study of ex-smokers in the 1980s, before the advent of pharmacotherapy, 53% of the ex-smokers said that it was "not at all difficult" to stop, 27% said it was "fairly difficult", and the remaining 20% found it very difficult. Studies have found that two-thirds of recent quitters reported using the cold turkey method and found it helpful.

Medications

The American Cancer Society notes that "Studies in medical journals have reported that about 25% of smokers who use medicines can stay smoke-free for over 6 months." Single medications include:

Nicotine replacement therapy (NRT): Five medications approved by the U.S. Food and Drug Administration (FDA) deliver nicotine in a form that does not involve the risks of smoking. NRTs are meant to be used for a short period of time and should be tapered down to a low dose before stopping. The five NRT medications, which in a Cochrane review increased the chances of stopping smoking by 50 to 70% compared to placebo or to no treatment, are: transdermal nicotine patches, gum, lozenges, sprays, and inhalers.

A Cochrane review found further increased chance of success in a combination of the nicotine patch and a faster acting form. A study found that 93 percent of over-the-counter NRT users relapse and return to smoking within six months.

Antidepressants: The antidepressant bupropion is considered a first-line medication for smoking cessation and has been shown in many studies to increase long-term success rates. People who take bupropion should be monitored for any unusual mood changes; bupropion also increases risk of seizures and should not be used in people with a seizure disorder. Nortriptyline has also been shown to increase smoking cessation success rates. In a recent Cochrane update, Nortiptyline did not produce significant rates of abstinence versus placebo, nor evidence of additional benefit when combined with NRT, although only four trials were included in the analysis.

Other antidepressants such as selective serotonin reuptake inhibitors (SSRIs) and St. John's wort have not been consistently shown to be effective for smoking cessation.

Varenicline decreases the urge to smoke and reduces withdrawal symptoms and is therefore considered a first-line medication for smoking cessation. A 2016 Cochrane review of 27 studies also found that the number of people stopping smoking with varenicline was higher than with bupropion or NRT. Varenicline more than doubled the chnaces of quitting compared to placebo; but was also as effective as combining tow types of NRT. 2 mg/day of varenicline has been found to lead to the highest abstinence rate (33.2%) of any single therapy, while 1 mg/day leads to an abstinence rate of 25.4%. A 2011 review of double-blind studies found that varenicline has increased risk of serious adverse cardiovascular events compared with placebo. Varenicline may cause neuropsychiatric side effects, including suicidal thoughts and behavior. However, more recent studies indicate less serious neuropsychiatric side effects. For example, a 2016 study involving 8,144 patients treated at 140 centers in 16 countires "did not show a significant increase in neuropsychiatric adverse events attributable to varenicline or bupropion relative to nicotine patch or placebo,".

Clonidine may reduce withdrawal symptoms and "approximately doubles abstinence rates when compared to a placebo," but its side effects include dry mouth and sedation, and abruptly stopping the drug can cause high blood pressure and other side effects.,.

The 2008 US Guideline specifies that three combinations of medications are effective:

Long-term nicotine patch and ad libitum NRT gum or spray

Nicotine patch and nicotine inhaler

Nicotine patch and bupropion (the only combination that the US FDA has approved for smoking cessation)

Cut down to quit

Gradual reduction involves slowly reducing one's daily intake of nicotine. This can theoretically be accomplished through repeated changes to cigarettes with lower levels of nicotine, by gradually reducing the number of cigarettes smoked each day, or by smoking only a fraction of a cigarette on each occasion. A 2009 systematic review by researchers at the University of Birmingham found that gradual nicotine replacement therapy could be effective in smoking cessation. There is no significant difference in quit rates between smokers who quit by gradual reduction or abrupt cessation as measured by abstinence from smoking of at least six months from the quit day, suggesting that people who want to quit can choose between these two methods.

Set a Quit Plan and Quit Date

Most smoking cessation resources such as the CDC and Mayo Clinic encourage smokers to create a quit plan, including setting a quit date, which helps them anticipate and plan ahead for smoking challenges. A quit plan can improve a smoker’s chance of a successful quit as can as setting Monday as the quit date, given that research has shown that Monday more than any other day is when smokers are seeking information online to quit smoking and calling state quit lines.

Community interventions

A Cochrane review found evidence that community interventions using "multiple channels to provide reinforcement, support and norms for not smoking" had an effect on smoking cessation outcomes among adults. Specific methods used in the community to encourage smoking cessation among adults include:

Policies making workplaces and public places smoke-free. It is estimated that "comprehensive clean indoor laws" can increase smoking cessation rates by 12%–38%. In 2008, the New York State of Alcoholism and Substantance Abuse Services banned smoking by patients, staff and volunteers at 1,300 addiction treatment centers.

Voluntary rules making homes smoke-free, which are thought to promote smoking cessation.

Initiatives to educate the public regarding the health effects of second-hand smoke, including the significant dangers of secondhand smoke infiltration for residents of multi-unit housing.

Increasing the price of tobacco products, for example by taxation. The US Task Force on Community Preventive Services found "strong scientific evidence" that this is effective in increasing tobacco use cessation It is estimated that an increase in price of 10% will increase smoking cessation rates by 3–5%.

Mass media campaigns. The US Task Force on Community Preventive Services declared that "strong scientific evidence" existed for these when "combined with other interventions", but a Cochrane review concluded that it was "difficult to establish their independent role and value".

Institutional level smoking bans. A recent Cochrane Review found evidence that imposing bans at the institutional level (i.e. hospitals and prisons) reduced smoking rates and secondhand exposure, although the evidence base was rated as poor quality.

Psychosocial approaches

Great American Smokeout is an annual event that invites smokers to quit for one day, hoping they will be able to extend this forever.

The World Health Organization's World No Tobacco Day is held on May 31 each year.

Smoking-cessation support is often offered over the telephone quitlines (e.g., the US toll-free number 1-800-QUIT-NOW), or in person. Three meta-analyses have concluded that telephone cessation support is effective when compared with minimal or no counselling or self-help, and that telephone cessation support with medication is more effective than medication alone.

Online social cessation networks attempt to emulate offline group cessation models using purpose built web applications. They are designed to promote online social support and encouragement for smokers when (usually automatically calculated) milestones are reached. Early studies have shown social cessation to be especially effective with smokers aged 19–29.

Group or individual psychological support can help people who want to quit. This form of counselling can be effective alone; combining it with medication is more effective, and the number of sessions of support with medication correlates with effectiveness. The counselling styles that have been effective in smoking cessation activities include motivational interviewing, cognitive behavioural therapy and Acceptance and Commitment Therapy.

The Freedom From Smoking group clinic includes eight sessions and features a step-by-step plan for quitting smoking. Each session is designed to help smokers gain control over their behavior. The clinic format encourages participants to work on the process and problems of quitting both individually and as part of a group.

Multiple formats of psychosocial interventions increase quit rates: 10.8% for no intervention, 15.1% for one format, 18.5% for 2 formats, and 23.2% for three or four formats.

The Transtheoretical Model including "stages of change" has been used in tailoring smoking cessation methods to individuals. However, a 2010 Cochrane review concluded that "stage-based self-help interventions (expert systems and/or tailored materials) and individual counselling were neither more nor less effective than their non-stage-based equivalents."

Self-help

A 2005 Cochrane review found that self-help materials may produce only a small increase in quit rates. In the 2008 Guideline, "the effect of self-help was weak," and the number of types of self-help did not produce higher abstinence rates. Nevertheless, self-help modalities for smoking cessation include:

In-person self-help groups such as Nicotine Anonymous, or web-based cessation resources such as Smokefree.gov, which offers various types of assistance including self-help materials.

WebMD: a resource providing health information, tools for managing health, and support.

Interactive web-based and stand-alone computer programs and online communities which assist participants in quitting. For example, "quit meters" keep track of statistics such as how long a person has remained abstinent. In the 2008 US Guideline, there was no meta-analysis of computerised interventions, but they were described as "highly promising." A meta-analysis published in 2009, a Cochrane review updated in 2013, and a 2011 systematic review found the evidence base for such interventions weak, although interactive and tailored interventions show some promise.

Mobile phone-based interventions: A 2016 updated Cochrane review stated that "the current evidence supports a beneficial impact of mobile phone-based cessation interventions on six-month cessation outcomes. A 2011 randomized trial of mobile phone-based smoking cessation support in the UK found that a Txt2Stop cessation program significantly improved cessation rates at 6 months. A 2013 meta-analysis also noted "modest benefits" of mobile health interventions.

Interactive web-based programs combined with Mobile phone: Two RCTs documented long-term treatment effects (abstinence rate: 20-22 %) of such interventions,.

Self-help books such as Allen Carr's Easy Way to Stop Smoking.

Spirituality: In one survey of adult smokers, 88% reported a history of spiritual practice or belief, and of those more than three-quarters were of the opinion that using spiritual resources may help them quit smoking.

A review of mindfulness training as a treatment for addiction showed reduction in craving and smoking following training.

Biochemical feedback

Various methods exist which allow a smoker to see the impact of their tobacco use, and the immediate effects of quitting. Using biochemical feedback methods can allow tobacco-users to be identified and assessed, and the use of monitoring throughout an effort to quit can increase motivation to quit. A recent Cochrane Review found "little evidence about the effects of most types of biomedical tests for risk assessment on smokign cessation,".

Breath carbon monoxide (CO) monitoring: Because carbon monoxide is a significant component of cigarette smoke, a breath carbon monoxide monitor can be used to detect recent cigarette use. Carbon monoxide concentration in breath has been shown to be directly correlated with the CO concentration in blood, known as percent carboxyhemoglobin. The value of demonstrating blood CO concentration to a smoker through a non-invasive breath sample is that it links the smoking habit with the physiological harm associated with smoking. Within hours of quitting, CO concentrations show a noticeable decrease, and this can be encouraging for someone working to quit. Breath CO monitoring has been utilized in smoking cessation as a tool to provide patients with biomarker feedback, similar to the way in which other diagnostic tools such as the stethoscope, the blood pressure cuff, and the cholesterol test have been used by treatment professionals in medicine.

Cotinine: A metabolite of nicotine, cotinine is present in smokers. Like carbon monoxide, a cotinine test can serve as a reliable biomarker to determine smoking status. Cotinine levels can be tested through urine, saliva, blood, or hair samples, with one of the main concerns of cotinine testing being the invasiveness of typical sampling methods.

While both measures offer high sensitivity and specificity, they differ in usage method and cost. As an example, breath CO monitoring is non-invasive, while cotinine testing relies on a bodily fluid. These two methods can be used either alone or together, for example, in a situation where abstinence verification needs additional confirmation.

Competitions and incentives

A 2011 Cochrane review concluded that, "incentives and competitions have not been shown to enhance long-term cessation rates,". A different 2008 Cochrane review found that one type of competition, "Quit and Win," did increase quit rates among participants.

Healthcare systems

Interventions delivered via healthcare providers and healthcare systems have been shown to improve smoking cessation among people who visit those services.

A clinic screening system (e.g., computer prompts) to identify whether or not a person smokes doubled abstinence rates, from 3.1% to 6.4%. Similarly, the Task Force on Community Preventive Services determined that provider reminders alone or with provider education are effective in promoting smoking cessation.

A 2008 Guideline meta-analysis estimated that physician advice to quit smoking led to a quit rate of 10.2%, as opposed to a quit rate of 7.9% among patients who did not receive physician advice to quit smoking. A Cochrane review found that even brief advice from physicians had "a small effect on cessation rates,". However, one study from Ireland involving vignettes found that physicians' probability of giving smoking cessation advice declines with the patient's age, and another study from the U.S. found that only 81% of smokers age 50 or greater received advice on quitting from their physicians in the preceding year.

For one-to-one or person-to-person counselling sessions, the duration of each session, the total amount of contact time, and the number of sessions all correlated with the effectiveness of smoking cessation. For example, "Higher intensity" interventions (>10 minutes) produced a quit rate of 22.1% as opposed to 10.9% for "no contact" over 300 minutes of contact time produced a quit rate of 25.5% as opposed to 11.0% for "no minutes" and more than 8 sessions produced a quit rate of 24.7% as opposed to 12.4% for 0–1 sessions.

Both physicians and non-physicians increased abstinence rates compared with self-help or no clinicians. For example, a Cochrane review of 35 studies found that nursing interventions increased the likelihood of quitting.

Dental professionals also provide a key component in increasing tobacco abstinence rates in the community through counseling patients on the effects of tobacco on oral health in conjunction with an oral exam.

According to the 2008 Guideline, based on two studies the training of clinicians in smoking cessation methods may increase abstinence rates; however, a Cochrane review found and measured that such training decreased smoking in patients.

Reducing or eliminating the costs of cessation therapies for smokers increased quit rates in three meta-analyses.

In one systematic review and meta-analysis, multi-component interventions increased quit rates in primary care settings. "Multi-component" interventions were defined as those that combined two or more of the following strategies known as the "5 A's":

Ask — Systematically identify all tobacco users at every visit

Advise — Strongly urge all tobacco users to quit

Assess — Determine willingness to make a quit attempt

Assist — Aid the patient in quitting (provide counselling-style support and medication)

Arrange — Ensure follow-up contact

Substitutes for cigarettes

Nicotine replacement therapy (NRT) is the general term for using products that contain nicotine but not tobacco to aid cessation of smoking. These include nicotine lozenges that are sucked, nicotine gum and inhalers, nicotine patches, as well as electronic cigarettes.

Electronic cigarette: In 2016 The Royal College of Physicians in London published an article advocating the use of electronic cigarettes as a smoking cessation tool and reporting that "e-cigarettes could lead to significant falls in the prevalence of smoking in the UK, prevent many deaths and episodes of serious illness, and helpt o reduce the social inequalities in health that tobacco smoking currently exacerbates,". A study conducted by Public Health England indicated that electronic cigarettes were 95% less harmful to people than smoking. They concluded that more research was needed, but electronic cigarettes could be a very useful smoking cessation tool in the future. A less recent research study, “Electronic cigarettes for smoking cessation: a randomized controlled trial", funded by the Health Research Council of New Zealand, was far less convinced that e-cigarettes were as viable an option as traditional modalities. The study was conducted between Sept 6,2011 and July 5, 2013, with a sample size of 657. Their interpretation of the results:
"E-cigarettes, with or without nicotine-based ejuices, were modestly effective at helping smokers to quit, with similar achievement of abstinence as with nicotine patches, and few adverse events. Uncertainty exists about the place of e-cigarettes in tobacco control, and more research is urgently needed to clearly establish their overall benefits and harms at both individual and population levels,".

Recent research has focused on the potential for e-cigarette use to increase the risk of subseqent initiation of combustible cigarette use among youth and Cancer Research UK has "declared the regulation of e-cigarettes a 'child protection issue',".

Chewing cinnamon sticks or gum has been recommended when trying to quit the use of tobacco.

Alternative approaches

Acupuncture: Acupuncture has been explored as an adjunct treatment method for smoking cessation. A 2014 Cochrane review was unable to make conclusions regarding acupuncture as the evidence is poor. A 2008 guideline found no difference between acupuncture and placebo, found no scientific studies supporting laser therapy based on acupuncture principles but without the needles.

Aromatherapy: A 2006 book reviewing the scientific literature on aromatherapy identified only one study on smoking cessation and aromatherapy; the study found that "inhalation of vapor from black pepper extract reduces smoking withdrawal symptoms,".

Hypnosis: Hypnosis often involves the hypnotherapist suggesting to the patient the unpleasant outcomes of smoking. Clinical trials studying hypnosis and hypnotherapy as a method for smoking cessation have been inconclusive; however, a randomized trial published in 2008 found that hypnosis and nicotine patches "compares favorably" with standard behavioral counseling and nicotine patches in 12-month quit rates.

Herbs: Many herbs have been studied as a method for smoking cessation, including lobelia and St John's wort,. The results are inconclusive, but St. Johns Wort shows few adverse events. Lobelia has been used to treat respiratory diseases like asthma and bronchitis, and has been used for smoking cessation because of chemical similarities to tobacco; lobelia is now listed in the FDA's Poisonous Plant Database. Lobelia can still be found in many products sold for smoking cessation and should be used with caution.

Psilocybin: One pilot study of 15 participants who had previously found it difficult to quit smoking found that 12 of them were able to quit smoking for at least 6 months after a cessation program that included closely administered use of pharmaceutical-grade psilocybin pills.

Smokeless tobacco: There is little smoking in Sweden, which is reflected in the very low cancer rates for Swedish men. Use of snus (a form of steam-pasteurised, rather than heat-pasteurised, air-cured smokeless tobacco) is an observed cessation method for Swedish men and even recommended by some Swedish doctors. However, the report by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR)conclues "STP (smokeless tobacco products) are addictive and their use is hazardous to health. Evidence on the effectiveness of STP as a smoking cessation aid is insufficient,". A recent national study on the use of alternative tobacco products, including snus, did not show that these products promote cessation.

Children and adolescents

Methods used with children and adolescents include:

Motivational enhancement

Psychological support

Youth anti-tobacco activities, such as sport involvement

School-based curricula, such as life-skills training

School-based nurse counseling sessions

Access reduction to tobacco

Anti-tobacco media,

Family communication

A Cochrane review, mainly of studies combining motivational enhancement and psychological support, concluded that "complex approaches" for smoking cessation among young people show promise. The 2008 US Guideline recommends counselling-style support for adolescent smokers on the basis of a meta-analysis of seven studies. Neither the Cochrane review nor the 2008 Guideline recommends medications for adolescents who smoke.

Pregnant women

Smoking during pregnancy can cause adverse health effects in both the woman and the fetus. The 2008 US Guideline determined that "person-to-person psychosocial interventions" (typically including "intensive counseling") increased abstinence rates in pregnant women who smoke to 13.3%, compared with 7.6% in usual care. Mothers who smoke during pregnancy have a greater tendency towards premature births. Their babies are often underdeveloped, have smaller organs, and weigh much less compared with the normal baby. In addition, these babies have worse immune systems, making them more susceptible to many diseases in early childhood, such as middle ear inflammations and asthmatic bronchitis which can bring about a lot of agony and suffering. As well, there is a high chance that they will become smokers themselves when grown up. A systematic review showed that psychosocial interventions help woman stop smoking in late pregnancy and can reduce the incidence of low birthweight infants.

It is a widely spread myth that a female smoker can cause harm to her fetus by quitting immediately upon discovering that she is with child. Though this idea does seem to follow logic, it is not based on any medical study or fact.

Workers

A 2008 Cochrane review of smoking cessation activities in work-places concluded that "interventions directed towards individual smokers increase the likelihood of quitting smoking,". A 2010 systematic review determined that worksite incentives and competitions needed to be combined with additional interventions to produce significant increases in smoking cessation rates.

Hospitalized smokers

Smokers who are hospitalised may be particularly motivated to quit. A 2012 Cochrane review found that interventions beginning during a hospital stay and continuing for one month or more after discharge were effective in producing abstinence.

Mood disorders

People who have mood disorders or attention deficit hyperactivity disorders have a greater chance to begin smoking and lower chance to quit smoking.

Comparison of success rates

Comparison of success rates across interventions can be difficult because of different definitions of "success" across studies. Robert West and Saul Shiffman, authorities in this field recognized by government health departments in a number of countries, have concluded that, used together, "behavioral support" and "medication" can quadruple the chances that a quit attempt will be successful.

A 2008 systematic review in the European Journal of Cancer Prevention found that group behavioural therapy was the most effective intervention strategy for smoking cessation, followed by bupropion, intensive physician advice, nicotine replacement therapy, individual counselling, telephone counselling, nursing interventions, and tailored self-help interventions; the study did not discuss varenicline.

Factors affecting success

Quitting can be harder for individuals with dark pigmented skin compared to individuals with pale skin since nicotine has an affinity for melanin-containing tissues. Studies suggest this can cause the phenomenon of increased nicotine dependence and lower smoking cessation rate in darker pigmented individuals.

There is an important social component to smoking. A 2008 study of a densely interconnected network of over 12,000 individuals found that smoking cessation by any given individual reduced the chances of others around them lighting up by the following amounts: a spouse by 67%, a sibling by 25%, a friend by 36%, and a coworker by 34%. Nevertheless, a Cochrane review determined that interventions to increase social support for a smoker's cessation attempt did not increase long-term quit rates.

Smokers who are trying to quit are faced with social influences that may persuade them to conform and continue smoking. Cravings are easier to detain when one's environment does not provoke the habit. If a person who stopped smoking has close relationships with active smokers, he or she is often put into situations that make the urge to conform more tempting. However, in a small group with at least one other not smoking, the likelihood of conformity decreases. The social influence to smoke cigarettes has been proven to rely on simple variables. One researched variable depends on whether the influence is from a friend or non-friend. The research shows that individuals are 77% more likely to conform to non-friends, while close friendships decrease conformity. Therefore, if an acquaintance offers a cigarette as a polite gesture, the person who has stopped smoking will be more likely to break his commitment than if a friend had offered. Recent research from the International Tobacco Control (ITC) Four Country Survey of over 6,000 smokers found that smokers with fewer smoking friends were more likely to intend to quit and to succeed in their quit attempt.

Expectations and attitude are significant factors. A self-perpetuating cycle occurs when a person feels bad for smoking yet smokes to alleviate feeling bad. Breaking that cycle can be a key in changing the sabotaging attitude.

Smokers with major depressive disorder may be less successful at quitting smoking than non-depressed smokers.

Relapse (resuming smoking after quitting) has been related to psychological issues such as low self-efficacy, or non-optimal coping responses; however, psychological approaches to prevent relapse have not been proven to be successful. In contrast, varenicline may help some relapsed smokers.

Symptoms

In a 2007 review of the effects of abstinence from tobacco, Hughes concluded that "anger, anxiety, depression, difficulty concentrating, impatience, insomnia, and restlessness are valid withdrawal symptoms that peak within the first week and last 2–4 weeks." In contrast, "constipation, cough, dizziness, increased dreaming, and mouth ulcers" may or may not be symptoms of withdrawal, while drowsiness, fatigue, and certain physical symptoms ("dry mouth, flu symptoms, headaches, heart racing, skin rash, sweating, tremor") were not symptoms of withdrawal.

Weight gain

Giving up smoking is associated with an average weight gain of 4–5 kilograms (8.8–11.0 lb) after 12 months, most of which occurs within the first three months of quitting.

The possible causes of the weight gain include:

Smoking over-expresses the gene AZGP1 which stimulates lipolysis, so smoking cessation may decrease lipolysis.

Smoking suppresses appetite, which may be caused by nicotine's effect on central autonomic neurons (e.g., via regulation of melanin concentrating hormone neurons in the hypothalamus).

Heavy smokers are reported to burn 200 calories per day more than non-smokers eating the same diet. Possible reasons for this phenomenon include nicotine's ability to increase energy metabolism or nicotine's effect on peripheral neurons.

The 2008 Guideline suggests that sustained-release bupropion, nicotine gum, and nicotine lozenge be used "to delay weight gain after quitting." However, a 2012 Cochrane review concluded that "The data are not sufficient to make strong clinical recommendations for effective programmes" for preventing weight gain.

Depression

Like other physically addictive drugs, nicotine addiction causes a down-regulation of the production of dopamine and other stimulatory neurotransmitters as the brain attempts to compensate for the artificial stimulation caused by smoking. Therefore, when people stop smoking, depressive symptoms such as suicidal tendencies or actual depression may result, although a recent international study comparing smokers who had stopped for 3 months with continuing smokers found that stopping smoking did not appear to increase anxiety or depression. This side effect of smoking cessation may be particularly common in women, as depression is more common among women than among men.

Anxiety

A recent study by The British Journal of Psychiatry has found that smokers who successfully quit feel less anxious afterward with the effect being greater among those who had mood and anxiety disorders than those that smoked for pleasure.

Health benefits

Many of tobacco's detrimental health effects can be reduced or largely removed through smoking cessation. The health benefits over time of stopping smoking include:

Within 20 minutes after quitting, blood pressure and heart rate decrease

Within 12 hours, carbon monoxide levels in the blood decrease to normal

Within 48 hours, nerve endings and sense of smell and taste both start recovering

Within 3 months, circulation and lung function improve

Within 9 months, there are decreases in cough and shortness of breath

Within 1 year, the risk of coronary heart disease is cut in half

Within 5 years, the risk of stroke falls to the same as a non-smoker, and the risks of many cancers (mouth, throat, esophagus, bladder, cervix) decrease significantly

Within 10 years, the risk of dying from lung cancer is cut in half, and the risks of larynx and pancreas cancers decrease

Within 15 years, the risk of coronary heart disease drops to the level of a non-smoker; lowered risk for developing COPD (chronic obstructive pulmonary disease)

The British Doctors Study showed that those who stopped smoking before they reached 30 years of age lived almost as long as those who never smoked. Stopping in one's sixties can still add three years of healthy life. A randomized trial from the U.S. and Canada showed that a smoking cessation program lasting 10 weeks decreased mortality from all causes over 14 years later. A recent article on mortality in a cohort of 8,645 smokers who were followed-up after 43 years determined that “current smoking and lifetime persistent smoking were associated with an increased risk of all-cause, CVD [cardiovascular disease], COPD [chronic obstructive pulmonary disease], and any cancer, and lung cancer mortality.

Another published study, "Smoking Cessation Reduces Postoperative Complications: A Systematic Review and Meta-analysis," examined six randomized trials and 15 observational studies to look at the effects of preoperative smoking cessation on postoperative complications. The findings were: 1) taken together, the studies demonstrated decreased the likelihood of postoperative complications in patients who ceased smoking prior to surgery; 2) overall, each week of cessation prior to surgery increased the magnitude of the effect by 19%. A significant positive effect was noted in trials where smoking cessation occurred at least four weeks prior to surgery; 3) For the six randomized trials, they demonstrated on average a relative risk reduction of 41% for postoperative complications.

Cost-effectiveness

Cost-effectiveness analyses of smoking cessation activities have shown that they increase quality-adjusted life years (QALYs) at costs comparable with other types of interventions to treat and prevent disease. Studies of the cost-effectiveness of smoking cessation include:

In a 1997 U.S. analysis, the estimated cost per QALY varied by the type of cessation approach, ranging from group intensive counselling without nicotine replacement at $1108 per QALY to minimal counselling with nicotine gum at $4542 per QALY.

A study from Erasmus University Rotterdam limited to people with chronic obstructive pulmonary disease found that the cost-effectiveness of minimal counselling, intensive counselling, and drug therapy were €16,900, €8,200, and €2,400 per QALY gained respectively.

Among National Health Service smoking cessation clients in Glasgow, pharmacy one-to-one counselling cost £2,600 per QALY gained and group support cost £4,800 per QALY gained.

Statistical trends

The frequency of smoking cessation among smokers varies across countries. Smoking cessation increased in Spain between 1965 and 2000, in Scotland between 1998 and 2007, and in Italy after 2000. In contrast, in the U.S. the cessation rate was "stable (or varied little)" between 1998 and 2008, and in China smoking cessation rates declined between 1998 and 2003.

Nevertheless, in a growing number of countries there are now more ex-smokers than smokers For example, in the U.S. as of 2010, there were 47 million ex-smokers and 46 million smokers. In 2014, the Centers for Disease Control and Prevention reports that the number of adult smokers, 18 years and older, in the U.S. has fallen to 40 million current smokers.