1 to 2 weeks headaches 1 to 2 weeks chest discomfort 1 to 2 weeks constipation 1 to 2 weeks irritability 2 to 4 weeks fatigue 2 to 4 weeks cough or nasal drip few weeks lack of concentration few weeks hunger up to several weeks withdrawal symptoms the cdc recognizes seven common nicotine withdrawal symptoms that people often face when stopping smoking: "cravings to smoke, feeling irritated, grouchy, or upset, feeling jumpy and restless, having a hard time concentrating, having trouble sleeping, feeling hungry or gaining weight, or feeling anxious, sad or depressed." studies have shown that the use of pharmacotherapies, such as varenicline can be useful in reducing withdrawal symptoms during the quitting process. 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). smoking cessation will increase the persons appetite once again, especially as taste buds can return to its normal function. 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 u.s. department of health and human services guideline suggests that sustained-release bupropion, nicotine gum, and nicotine lozenge be used "to delay weight gain after quitting." there is not currently enough evidence to suggest one method of weight loss works better than others in preventing weight gain during the smoking cessation process. it is helpful to reach for healthy snacks, such as celery and carrots, to aid in the increased appetite while also helping to limit weight gain. regardless of post-cessation weight gain, there is a significant decrease in risk of cardiovascular disease in those who have quit smoking. the risks of rebound weight gain is significantly less than the risks of continued smoking. mental health 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. some studies from the 1990s found that 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. a 2021 review found that quitting smoking lessens anxiety and depression. a 2013 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 who smoked for pleasure. health benefits survival from age 35 of non-smokers, cigarette smokers and ex-smokers who stopped smoking between 25 and 34 years old. the ex-smokers line follows closely the non-smokers line. 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 a few days, 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 1 year, there are decreases in cough and shortness of breath within 1–2 years, the risk of coronary heart disease is cut in half within 5–10 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 old lived almost as long as those who never smoked. stopping in one's sixties can still add three years of healthy life. randomized u.s. and canadian trials showed that a ten-week smoking cessation program 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 , copd , and any cancer, and lung cancer mortality." the significant increase in the risk of all-cause mortality that is present in people who smoke is decreased with long-term smoking cessation. smoking cessation can improve health status and quality of life at any age. evidence shows that cessation of smoking reduces risk of lung, laryngeal, oral cavity and pharynx, esophageal, pancreatic, bladder, stomach, colorectal, cervical, and kidney cancer, in addition to reducing the risk of acute myeloid leukemia. another published study, "smoking cessation reduces postoperative complications: a systematic review and meta-analysis," examined six randomized trials and 15 observational studies to examine preoperative smoking cessation's effects on postoperative complications. the findings were: 1) taken together, the studies demonstrated a decreased likelihood of postoperative complications in patients who ceased smoking before surgery; 2) overall, each week of cessation before 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 before surgery; 3) for the six randomized trials, they demonstrated, on average, a relative risk reduction of 41% for postoperative complications. cost-effectiveness smokers as a percentage of the population for the united states, the netherlands, norway, japan, and finland 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.: 134–137 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. in the united states, 61.7% of adult smokers (55.0 million adults) who had ever smoked had quit by 2018, an increase from 51.7% in 2009. as of 2020, the cdc reports that the number of adults who smoke in the u.s. has fallen to 30.8 million.