- Smoking kills more than 5 million people a year worldwide, accounting for 1 out of every 10 adult deaths, according to the World Health Organization.
- Up to half of all current smokers will die from a tobacco-related disease.
- Fewer teens are smoking now than in the late 1990s, but the decrease in teen smoking rates has been slower in recent years. Today, 46% of high school students have ever smoked cigarettes, down from 70% in 1991. The number of frequent smokers (20 or more cigarettes a month) dropped from about 13% in 1991 to 7% in 2009.
- People who smoke pipes or cigars are at increased risk for lung damage and chronic obstructive pulmonary disease (COPD), even if they never smoked cigarettes.
- Combining a nicotine patch with a nicotine lozenge is most effective at helping smokers quit, according to researchers who compared six different quit smoking therapies.
- Having depression increases the likelihood that someone will smoke, and decreases their likelihood of quitting. Forty-three percent of adults with depression are current smokers, compared to only 22% of those without depression. The more severe their depression, the more likely people are to smoke.
- Smoking is the second leading risk factor for age-related macular degeneration (AMD), after age. Smokers have 11% higher rates of AMD than nonsmokers of the same age.
- In women who are worried about gaining weight after they quit smoking, combining behavioral therapy for smoking-related weight concerns with the antidepressant bupropion can help them stop smoking for longer.
Other Health Effects of Smoking:
- Up to 90% of lung cancer deaths are attributed to smoking.
- Smoking greatly increases a person's risk of heart attacks and strokes.
- COPD is directly related to smoking.
- Smoking greatly increases the smoker's risk of oral and esophageal cancers.
- Women who smoke tend to start menopause at an earlier age than nonsmokers, perhaps because toxins in cigarette smoke damage eggs.
- Women who smoke have a greater risk for ectopic pregnancy and miscarriage.
- Smoking clearly increases the risk of colorectal cancer and aggressive colon polyps, which are considered precursors to colon cancer.
- The following age-related conditions occur at higher rates in smokers than nonsmokers:
- AMD, a leading cause of blindness in older people
- Hearing loss
More than 46 million, nearly 21% of adults in the United States, smoke, according to a 2010 report by the U.S. Centers for Disease Control and Prevention (CDC). Smoking rates remained constant from 2005 - 2009.
Smoking kills more than 5 million people a year worldwide, accounting for 1 out of every 10 adult deaths.
The addictive effects of tobacco have been well documented. Tobacco is considered to be a mood and behavior altering substance that is psychoactive and abusable. Tobacco is believed to be as potentially addictive as alcohol, cocaine, and morphine. Tobacco and its various components increase the risk of cancer (especially in the lung, mouth, larynx, esophagus, bladder, kidney, colon, pancreas, and cervix), heart attacks, strokes, and chronic lung disease.
Smoking in Childhood and Adolescence
Fewer teens are smoking today than in the late 1990s, but the decrease in teen smoking rates has been slower in recent years. Today 46% of high school students have ever smoked, down from 70% in 1991. The number of frequent smokers (defined as 20 or more cigarettes a month) dropped from about 13% in 1991 to 7% in 2009.
The younger children start smoking, the more likely they will smoke as adults. Smoking is often rapidly addictive. According to the American Cancer Society, the earlier you start smoking, the more likely you are to develop long-term nicotine addiction.
In the past, advertising played a major role in encouraging some teens to smoke. New regulations have made it much more difficult for advertisers to promote smoking to young people. However, scenes that show people smoking, often in a positive way, are still common in movies and television shows. This may be a major influence on the attitude toward smoking in children and adolescents.
To prevent children from smoking, parents should not smoke, and they should tell their child that they disapprove of smoking. Studies have shown that schoolchildren who believed that both their parents strongly disapproved of smoking were less than half as likely to smoke as those kids whose parents did not show as much disapproval toward smoking.
Children whose parents closely monitor their television and music-listening habits are less likely to drink, use drugs, and smoke cigarettes.
Neglected children, or children with absentee parents, are four times as likely to abuse drugs, drink, and smoke as children living with parents who were regularly present and who offered a structured lifestyle.
Doctors can have a major effect on young people. However, less than half of teenagers say their doctors have ever asked them if they smoked, or that they have been counseled not to smoke, even though most teen smokers said they would admit to smoking if asked.
Of special concern are studies that directly link smoking in adolescents to suicide attempts in this age group. Teens who smoke are more likely to attempt suicide than their non-smoking peers.
Gender, Age, and Ethnicity
|18 - 24 years||21.8%|
|25 - 44 years||24.0%|
|45 - 64 years||21.9%|
|65 years and older||9.5%|
|Source: CDC/MMWR Report 2010|
While the number of adults over age 65 who smoke is lower than those in other age groups, older adults usually have smoked for a long time (about 40 years) and tend to be heavier smokers, according to the American Lung Association. Because of this, older smokers are more likely to have smoking-related illnesses.
Caucasian students (under age 18) are more likely to smoke than Hispanics and African-Americans. The rate of smoking is highest among people of mixed race, followed by American Indians and Alaskan natives. Asians have the lowest smoking rates.
In general, the rate of smoking is highest in the Midwest and South and lowest in the Northeast and West. Utah has the lowest smoking rate in the United States.
People who have not graduated from high school or received their General Education Development (GED) certificate tend to have higher smoking rates than those who attended college.
Higher rates of cigarette smoking have been reported among adults who have earned a GED and those with a grade 9 - 11 education. The lowest rates are seen among those with advanced graduate degrees.
People with low self-esteem and adolescents with behavioral problems have a higher risk for smoking. Men and women with mental disorders are 50% more likely to smoke than those without such illnesses. Schizophrenia and depression are known risk factors for smoking. Both mental disorders may have biological effects that lead to this higher risk.
Having depression increases the likelihood that someone will smoke, and decreases their likelihood of quitting. Twice as many adults with depression are current smokers, compared to those without depression. The more severe their depression, the more likely people are to smoke.
Smoking Among Persons with Disabilities
Smoking is much more common among persons with disabilities than those without emotional, mental, or physical limitations. The rate of smoking is nearly 50% higher among persons with disabilities.
Evidence strongly supports the idea that genes play a role in a person's dependence on nicotine. Researchers are now targeting specific genes that may be responsible for nicotine dependence. So far, research has shown that there is a common genetic vulnerability to both nicotine and alcohol dependence.
Some studies suggest that the cheaper it is to buy cigarettes and smoke, the more widespread smoking will be. For example, states that have low taxes on cigarettes have a high proportion of smokers. Making it more expensive to smoke may reduce the number of smokers.
Nicotine is the chemical in cigarettes that makes them addictive. About 85% of smokers are addicted to nicotine. Higher levels of nicotine in a cigarette can make it harder to quit smoking. The amount of nicotine in cigarettes has steadily increased in the past decade. Higher nicotine levels have been found in all cigarette categories, including "light" brands.
Some researchers feel nicotine is as addictive as heroin. In fact, nicotine has actions similar to heroin and cocaine, and the chemical affects the same area of the brain.
Depending on the amount taken in, nicotine can act as either a stimulant or a sedative. Cigarette smoking has definite immediate positive effects. For example, it can:
- Boost mood and relieve minor depression
- Suppress anger
- Enhance concentration and short-term memory
- Produce a modest sense of well-being
Most smokers have a special fondness for the first cigarette of the day because of the way brain cells respond to the day's first nicotine rush. Nicotine, particularly taken in the first few cigarettes of the day, increases the activity of dopamine, a chemical in the brain that elicits pleasurable sensations. This feeling is similar to getting a reward.
Over the course of a day, however, the nerve cells become desensitized to nicotine. Smoking becomes less pleasurable, and smokers may be likely to increase their intake to get their "reward." A smoker develops tolerance to these effects very quickly and requires increasingly higher levels of nicotine.
Smokeless tobacco, also called spit tobacco, includes chewing tobacco (dip and chew), tobacco powder (snuff), as well as flavored tobacco lozenges. These products also contain nicotine.
Smokeless tobacco products allow tobacco to be absorbed by the digestive system or through mucus membranes. Smokeless tobacco contains at least 28 cancer-causing substances, and is not a safe substitute for smoking cigarettes or cigars. According to the National Institutes of Health, chewing on an average-sized piece of chewing tobacco for 30 minutes can deliver as much nicotine as smoking three cigarettes.
Evidence suggests that smokeless tobacco increases the risk of oral cancer, gingivitis, and tooth loss. The risk of cancer in people who use smokeless tobacco is lower than that of smokers, but is still higher than that of people who do not use tobacco at all. Using smokeless tobacco also seems to increase the risk of fatal heart attacks and strokes.
Pipes and Cigars
Pipe and cigar smoking are on the rise. Because pipe and cigar smokers often don't inhale, the common misperception is that they don't face as substantial a health risk as cigarette smokers. Yet recent research finds that smoking pipes or cigars causes harmful health effects similar to those of cigarettes.
People who smoke pipes or cigars are at greater risk for lung damage and COPD, even if they never smoked cigarettes.
Smoking -- even just a few cigarettes a day -- has been linked to many serious health risks. Up to half of all current tobacco users will die from a tobacco-related disease, some of which are discussed below.
Effects on the Lungs
According to the American Lung Association, smoking is directly responsible for about 90% of the deaths due to lung cancer. Smoking is also responsible for the majority of deaths due to chronic obstructive pulmonary disease (COPD), which includes emphysema and chronic bronchitis.
Smoking reduces a person's ability to control their asthma, interfering with the response to steroid medicine and worsening lung function.
All forms of tobacco raise the risk for heart attacks. Smoking, chewing tobacco, and being exposed to secondhand smoke greatly increase the risk of heart attacks and strokes. In some cases, the risk of heart problems in people who smoke or who are exposed to smoke may be three times greater than that of people who don't smoke. The risk of a heart attack in people who stop smoking decreases over time.
Smoking also significantly increases the risk of peripheral artery disease, which damages the blood vessels in the legs and increases the risk of disability and even amputation.
Effects on Male Fertility and Erectile Dysfunction
Smoking can harm a man's sexuality and fertility. Heavy smoking is frequently cited as a contributing factor in erectile dysfunction because it decreases the amount of blood flowing into the penis.
Smoking impairs sperm motility, reduces sperm lifespan, and may cause genetic changes that can affect a man's offspring. Men and women who smoke have lower success rates with fertility treatments. Men who smoke also have a lower sex drive and less frequent sex.
Effects on Female Infertility, Pregnancy, and Childbirth
Studies have linked cigarette smoking to many reproductive problems. Continuing to smoke during pregnancy can also cause health problems in the baby.
Negative effects of smoking include:
- Greater risk for infertility. Women at greatest risk for fertility problems are those who smoke one or more packs a day and who started smoking before age 18.
- Earlier menopause. Women who smoke tend to start menopause at an earlier age than nonsmokers, perhaps because toxins in cigarette smoke damage eggs.
- Pregnancy complications, which increase with the number of cigarettes smoked.
Click the icon to see an image of an ectopic pregnancy.
Pregnancy complications that are more common in smokers include an increased chance of miscarriage and stillbirth, premature rupture of membranes, premature delivery, and problems with the placenta. Smoking further increases the risk to the mother and unborn child in high-risk pregnancies.
Effects on the Unborn Child. Smoking during pregnancy increases the risk for low birth weight. Women who smoke during pregnancy have lower levels of folate, a B vitamin that is important for preventing birth defects.
Children of mothers who smoke during pregnancy may also be at increased risk for obesity and diabetes.
Smoking during pregnancy seems to also increase the risk of having a baby with cleft lip (a split lip that has not closed during the fetus' development) or a neural tube defect.
Some women have particular genes that may make them especially likely to deliver low birth weight infants if they smoke, although newborns of all female smokers have a greater risk for low birth weight. The good news is that women who stop smoking before becoming pregnant or during their first trimester of pregnancy reduce their risk of having a low birth weight baby to that of women who never smoked.
Women who want to become pregnant should make every attempt to stop smoking, and they should use smoking cessation aids before they try to conceive. Government guidelines recommend that doctors ask all of their pregnant patients about their tobacco use, and offer counseling to those patients who do smoke. After birth, if new mothers cannot quit, they should at least be sure not to smoke in the same room as their infant.
Effects on Bones and Joints
Smoking has many harmful effects on bones and joints:
- Smoking can slow the process that adds calcium to bones and makes them stronger. Women who smoke are at high risk for bone density loss and osteoporosis.
Click the icon to see an image of osteoporosis.
- Postmenopausal women who smoke have a significantly greater risk for hip fracture than those who do not.
- Smokers are more apt to develop degenerative disorders and injuries in the spine.
- Smokers have more trouble recovering from surgeries.
Click the icon to see an image of rheumatoid arthritis.
Smoking and Diabetes
Smoking may increase the risk of developing diabetes or glucose intolerance, a condition that precedes diabetes.
Smoking and the Gastrointestinal Tract
Smoking increases acid production in the stomach. It also reduces blood flow and the production of compounds that protect the stomach lining.
Inflammatory Bowel Disease. Smoking has mixed effects on inflammatory bowel disease, the collective term for ulcerative colitis and Crohn's disease. Smokers have been shown to have lower-than-average rates of ulcerative colitis, but higher-than-average rates of Crohn's disease. Smokers with Crohn's disease who stop smoking have less severe symptoms than people who continue to smoke.
Click the icon to see an image of inflammatory bowel disease.
Colorectal cancer. Smoking increases the risk of colorectal cancer and aggressive colon polyps, which are considered precursors to colon cancer. The connection is stronger for rectal cancer than for colon cancer. Cigarette smoking is also a known risk factor for pancreatic cancer, and has been established as a major behavioral risk factor for gastric cancer.
Click the icon to see an image of peptic ulcers.
Hepatitis and Cirrhosis. Smoking is linked to increased liver scarring (cirrhosis) caused by either excessive drinking or chronic hepatitis B or C viruses.
Smoking and Thyroid Disease
Cyanide, a chemical found in tobacco smoke, interferes with thyroid hormone production. Smoking triples the risk for developing thyroid disease, particularly hyperthyroidism and hypothyroidism. Women smokers with subclinical hypothyroidism (a symptom-free condition in which the thyroid gland is mildly underactive) have a higher risk for developing full-blown hypothyroidism than their nonsmoking peers. Smoking has also been linked to goiter, a swelling of the thyroid that occurs in people who do not get enough iodine.
Click the icon to see an image of the thyroid.
Smoking and Surgical Recovery
Smokers are at increased risk for heart and circulatory problems and delayed wound healing after surgery. Patients who are able to cut down or quit smoking 6 - 8 weeks before knee or hip replacement surgery are much less likely to have complications.
Smoking and Age-Related Disorders
The following age-related conditions are thought to occur at higher rates in smokers than nonsmokers:
- Cataracts. Quitting smoking reduces your chances of needing cataract surgery in the future, although not to the level seen with nonsmokers.
Click the icon to see an image of a cataract.
- Age-related macular degeneration (AMD). AMD is a leading cause of blindness in older people. Symptoms of macular degeneration include a loss of central vision, which makes it difficult to read. Smoking is the second leading risk factor for AMD, after age. Heavy smoking over a long period of time can significantly increase AMD risk.
- Gum disease and tooth loss. One-half or more of the cases of severe gum disease in adults in the United States may be due to cigarette smoking.
- Wrinkles. Smokers are nearly five times more likely to develop more and deeper wrinkles as they age compared to nonsmokers.
- Baldness and premature gray hair. Certain chemicals in smoke break down in hair cells, which leads to hair damage.
- Hearing loss, particularly high-frequency hearing loss.
Secondhand smoke is produced by a burning cigarette or other tobacco product. About 88 million nonsmokers are exposed to secondhand smoke each year -- 32 million of them are children and adolescents. Parental smoking has been shown to affect the lungs of infants as early as the first 2 - 10 weeks of life, and such abnormal lung function could persist throughout life.
Being exposed to secondhand smoke increases the risk for heart attacks and lung cancer.
Exposure to secondhand smoke in the home increases the risk for asthma and asthma-related emergency room visits in children who have existing asthma. Children whose parents smoke are also more likely to be overweight and to have behavioral problems.
Parental smoking is believed to increase the risk for lower respiratory tract infections (such as bronchitis or pneumonia) by 50%. Environmental exposure to smoke is thought to be responsible for 150,000 - 300,000 such cases every year.
More and more households in the United States are banning smoking. The U.S. Centers for Disease Control and Prevention (CDC) reports that 75% of households now forbid smoking at any time or place in the home.
Smoking bans have spread across the country. At least 35 states have passed some type of law banning smoking in almost all public places and workplaces, including restaurants and bars.
The risk of heart attacks in communities enforcing such bans has decreased 17% overall. Younger people and non-smokers seem to benefit the most from such bans.
It's never too late to quit smoking. According to the American Cancer Society, about half of all smokers who keep smoking will die from a smoking-related disease. Quitting has immediate health benefits.
Better Health After Quitting
Time after last cigarette
Blood pressure and pulse rates return to normal.
Levels of carbon monoxide and oxygen in the blood return to normal.
Chance of a heart attack begins to decrease.
Nerve endings start to regrow. Your ability to taste and smell increases.
Bronchial tubes relax and the lungs can fill with more air.
2 weeks to 3 months
Improved circulation; lung function increases by up to 30%.
1 to 9 months
Decreased rates of coughing, sinus infection, fatigue, and shortness of breath; regrowth of cilia in the airways, improving the ability to clear mucus and clean the lungs and reducing the chance of infection; increased energy level.
After a year, the risk of dying from a heart attack or stroke is reduced by up to 50%.
According to the National Institutes of Health, about 40% of smokers who want to quit make a serious attempt to do so each year, but fewer than 5% actually succeed. Available smoking cessation products and therapies are greatly underused. If more smokers asked for or were offered such help, the agency says quit rates could double or triple.
Some people have certain genes that make quitting easier. Researchers have identified more than 200 genes that distinguish people who have successfully quit smoking. The discovery of these genes could lead to new smoking cessation therapies that target a person's specific genetic makeup.
Methods of quitting smoking include counseling and support groups, nicotine patches, gums, lozenges, and sprays, smoking cessation pills, and slowly cutting back on the number of cigarettes smoked (incremental reduction).
Nicotine Replacement Therapy
Nicotine replacement therapy involves the use of products that provide low doses of nicotine, without the contaminants found in smoke. The goal of therapy is to relieve cravings for nicotine and ease the symptoms of withdrawal.
In general, nicotine replacement therapy benefits moderate-to-heavy smokers the most. However, it does appear somewhat helpful for light smokers (people who smoke fewer than 15 cigarettes a day).
Combining nicotine replacement therapies may be more effective than using one alone. For example, a combination of the nicotine patch and nicotine gum, nasal spray, or lozenge helps smokers go smoke-free for a longer period of time before relapsing. Adding bupropion to nicotine replacement therapy also increases the chance for success.
Nicotine Patches. Nicotine patches deliver nicotine through the skin. This is called transdermal nicotine delivery. It is effective in reducing symptoms during withdrawal. Nicotine patches are available over the counter.
Patches may work in different ways:
- Step-Down Approach. Patches that use this method include NicoDerm CQ. The patches come in three strengths (21, 14, and 7 mg). You use the strongest dose first and reduce it gradually over a period of 8 - 10 weeks. A 21 mg patch is about equal to 15 cigarettes. A heavy smoker may need to wear two patches at first.
- Single-Step Approach. The single-step patch (Nicotrol) can be taken off after 16 hours and replaced 8 hours later. It can be used for only 6 weeks.
Patches are applied and used in similar ways:
- A single patch is worn each day and replaced after 24 hours.
- To avoid skin irritation it is applied to different hairless locations above the waist and below the neck each day.
- People can wear the patches for 24 hours, but some have reported odd dreams and have disliked the sensation of the patch during the night. People who wear the patch all the time, however, have fewer withdrawal symptoms and slightly better abstinence rates than those who take it off at night.
- Patches should be stored and discarded safely, particularly in homes with small children. Small children have been poisoned and gotten sick from wearing, chewing, or sucking on nicotine patches. There have been no reports of death in children who have been poisoned.
- The FDA recommends using the patches for 3 - 5 months, although some studies suggest that using them for 8 weeks achieves the maximum benefits.
Children should not come in contact with the patches, even while the smoker is wearing them. If a child puts on a patch, it should be removed and the affected skin should be washed right away. Urgent medical care may be required if the child has eaten nicotine or worn a patch for a prolonged time.
Nicotine Gum. Nicotine gum (Nicorette) is available over the counter and has helped many people quit. Some people prefer gum to the patch because they can control the nicotine dosage, and chewing satisfies the oral urge associated with smoking.
Tips for using the gum:
- If you are just starting to quit, chew 1 - 2 pieces every hour or two. Do not chew more than 24 pieces a day.
- Gradually taper off. The goal is to stop using the gum by 3 months, but about 3% of people continue to use it long after they have quit smoking.
- Chew the gum slowly until it develops a peppery taste. Then tuck it between the gum and cheek, so that the nicotine can be absorbed.
- Coffee, tea, soft drinks, and acidic beverages may interfere with nicotine absorption, so wait at least 15 minutes after drinking before chewing a piece of gum.
Some people prefer other methods or cannot use the gum for the following reasons:
- They find the taste of the gum unpleasant.
- Side effects of the gum may include upset stomach, mouth ulcers, hiccups, and throat irritation.
- They are embarrassed by chewing gum.
- They wear dentures.
Long-term dependence may be a problem with the gum. Although such dependence is probably safer than smoking, research is needed to confirm this, and experts do not recommend that people chew gum for more than 6 months.
The Nicotine Inhaler. The nicotine inhaler resembles a plastic cigarette holder. It comes with a number of nicotine cartridges, which are inserted into the inhaler and "puffed" for about 20 minutes, up to 16 times a day. The dose is gradually decreased. It requires a prescription in the United States. Several studies have reported that the inhaler triples abstinence rates (between 17 - 28%) compared with placebo (6 - 9%) after 6 months. It has some specific advantages over other nicotine replacement products:
- The inhaler provides varying doses of nicotine on demand (as opposed to continuous doses with the patch or gum) and is relatively fast-acting. Blood nicotine levels peak about 20 minutes after using the inhaler, comparable to the gum and faster than the 2 - 4 hours seen with the patch.
- It satisfies oral urges.
- Most of the nicotine vapor is delivered in the mouth, not into the lung airways (although some people experience mouth or throat irritation and a cough).
Using a combination of the inhaler and the patch may be particularly effective.
Electronic cigarettes (E-Cigarettes). Electronic cigarettes are cigarette-, cigar-, or pipe-shaped devices that deliver nicotine or other substances in the form of a vapor. Electronic cigarettes are marketed as as quit-smoking aids because they are designed to give the feeling of smoking without actually lighting up. However, the FDA cautions that electronic cigarettes have not been carefully evaluated for safety or effectiveness. In 2010, the FDA issued warning letters to five distributors of electronic cigarettes for violations including unsubstantiated claims and poor manufacturing processes. The agency wants manufacturers to conduct clinical studies to determine whether their products are actually safe and effective.
The Nicotine Nasal Spray. The nasal spray satisfies immediate cravings by providing doses of nicotine rapidly and thus may play a useful role in conjunction with slower-acting nicotine replacement therapies. (Nicotine levels peak within 5 - 10 minutes after administering the spray). The spray can irritate the nose, eyes, and throat, so it may not be suitable for those with allergies or sinus infections. Most people, however, can tolerate the side effects, which usually go away within the first few days.
Nicotine Lozenge. A nicotine lozenge (Commit) is available over the counter. It is made from pressed tobacco and comes in two strengths for heavier or lighter smokers. Suck on one piece every 1 - 2 hours, then gradually taper off your use. Don't eat or drink 15 minutes before using a lozenge, and don't take more than 20 lozenges a day. Side effects include heartburn, hiccups, nausea, headaches, and cough. The Commit lozenge also contains phenylalanine, a chemical that certain people may need to avoid.
Facts about Nicotine Replacement Therapy:
- Not cheating on the very first day of nicotine-replacement use increases the chance of quitting permanently tenfold.
- The more cigarettes people smoke, the higher the dose of nicotine replacement they may need at first.
- Adding a counseling program may boost the effectiveness of any nicotine replacement program.
- Do not smoke while using nicotine replacement. It can cause nicotine to build up to toxic levels in your body.
- Nicotine replacement helps prevent weight gain while you are using it, but you are still at higher risk for gaining weight when you stop using all nicotine.
Side Effects. Side effects of any nicotine replacement product may include headaches, nausea, and other gastrointestinal problems. People often experience sleeplessness in the first few days, particularly with the patch, but the insomnia usually passes. Patients using very high doses are more likely to have symptoms. Reducing the dose can prevent these symptoms.
Special Concerns for Specific Individuals. There has been some concern that the patch might be harmful for people with heart or circulatory disease, but studies are finding that it poses no danger for these individuals. In fact, the patch may help reduce angina attacks brought on by exercise. However, unhealthy cholesterol levels (lower HDL levels) caused by smoking remain abnormal with use of the nicotine patch. HDL levels improve when all nicotine is stopped.
Nicotine replacement may not be completely safe in pregnant women, although it has been used successfully in this group without ill effect. There is an increase in heart rates in the unborn children of women who use the patch as compared with those who smoke.
Keep all nicotine products away from children. Nicotine is a poison. All nicotine products should be kept safely away from small children. A parent should call a physician or a poison control center immediately if a child has been exposed to a nicotine replacement product, even for a short period of time. Parents should also call the doctor if a child has been exposed to a nicotine product and has any symptoms, including stomach upset, irritability, headaches, a rash, or fatigue.
Warnings Against Long-Term Use. No one should use nicotine replacement therapies as a long-term substitute for smoking. Any nicotine replacement therapy should be temporary.
Smoking Cessation Pills
Antidepressants. Bupropion (Zyban, Wellbutrin) is a type of antidepressant that is also an FDA-approved product for smoking cessation. It differs from most other antidepressants because it increases the effects of dopamine, the brain chemical that appears to play a strong role in nicotine addiction. Using bupropion along with nicotine replacement therapy may help you better control cigarette smoking cravings. Bupropion does not contain nicotine. In most cases, bupropion is started a week or two before quitting, and must be taken for 7 - 12 weeks. The usual maintenance dose is a 150 mg tablet twice a day. No single dose should be higher than 150 mg.
Side effects of bupropion include gastrointestinal problems, headaches, insomnia, dry mouth, and irritation. In very rare cases, seizures have occurred, although usually in people who exceeded the recommended dose or who already had risk factors for seizures.
Warning about Bupropion: In July 2009 the FDA required the makers of bupropion to add a Boxed Warning (the strongest possible warning) regarding serious mental health side effects that may occur while using the medication. These potentially serious side effects include "changes in behavior, hostility, agitation, depressed mood, suicidal thoughts and behavior, and attempted suicide." Patients taking this medication, as well as their family members, should be aware of these potential dangers and report any symptoms to their doctor immediately. Patients are also advised to stop taking the medication immediately if any of these symptoms occur.
The tricyclic antidepressant nortriptyline (Pamelor, Aventyl) may help reduce nicotine action. Quit rates with this medication are as high as 30%. Long-term abstinence rates are more than twice those of placebo. Most other antidepressants, including fluoxetine (Prozac), have no additional benefits for smokers.
Nortriptyline has been specifically studied for helping smokers. It is best to start taking the medication 10 - 28 days before your intended quit date. Side effects of nortriptyline include drowsiness, dry mouth, and changes in taste. In rare cases, tricyclic antidepressants can have serious side effects, and an overdose can be deadly. Tricyclics may pose a danger for patients with certain types of heart disease.
Varenicline. A newer drug called varenicline (Chantix) may significantly work better than bupropion. Unlike bupropion, it works on nicotine receptors in the brain, which helps reduce cravings. Varenicline can be used by cigarette smokers ages 18 and older. It should not be combined with nicotine replacement therapy. Nausea is one of the side effects.
Warning about Chantix: Varenicline carries a Boxed Warning regarding serious mental health side effects that may occur while using the medication, or immediately after stopping it. These uncommon but potentially serious side effects include "changes in behavior, agitation, depressed mood, suicidal ideation and suicidal behavior." Patients taking this medication, as well as their family members, should be aware of these potential dangers and report any symptoms to their doctor immediately. Patients are also advised to stop taking the medication immediately if any of these symptoms occur.
Behavioral Methods and Counseling
Everyone who quits should aim to quit completely. Most people who return to smoking "cheat" in the first few weeks. Quitting completely is essential to regaining good health and reversing the harmful effects caused by smoking. Reducing smoking, even by half, does not eliminate the risk for cancer and other health problems. Although smokers who cut back take in less smoke and nicotine, their bodies are still unable to heal completely from the ongoing intake of toxins. Changing to low-tar cigarettes is not a solution. In fact, people who smoke these cigarettes tend to inhale more deeply, perhaps even increasing their health risks.
Create a List
Write down 10 reasons to quit. In addition to health reasons, the list might include having better smelling hair, clothes, and breath; having fewer wrinkles; enjoying the taste of food; and saving money. Read the list often during the quitting process to help you stay motivated.
Decide on a Specific Quit Date
Some people find it helpful to choose a particular date to quit when they anticipate little or no stress for at least the first 3 days. Women affected by PMS should avoid quitting right before getting their period. It may help to write out a quit contract, putting the date on paper, and get a friend to sign it. Discard all smoking paraphernalia on the eve before the quit date, and make plans to stay busy on the day itself, especially at night, when the urge to smoke will be high.
If quitting cold turkey isn't for you, gradually stopping is an equally effective approach, according to research. Reducing the number of cigarettes you smoke before quit day might work just as well as stopping all at once.
Make an Oath
Take an extreme oath. For example, "If I smoke one more cigarette my dog will die." Although this seems absurd, some people, even well-educated individuals, who have failed all other methods have reported that they quit completely and successfully after taking such an oath.
Let the Body and Mind Heal During Withdrawal
- Retreat from the world when cravings become overwhelming. Take naps, warm baths or showers, meditate, or read novels.
- Help your body get rid of nicotine. Drink plenty of water; eat fresh fruits, vegetables, whole grains, and fiber-rich foods. Carrots, apples, and celery are good munching foods.
- When cravings occur, hold your breath for as long as possible, or take a few deep rhythmic breaths.
- Use meditation or relaxation and deep breathing exercises. In fact, taking deep breaths when the urge to smoke occurs is a good stopgap measure.
Get Family and Friends Involved
- Tell all your friends and family that you've already quit, so you'll be embarrassed if they catch you smoking.
- Fine yourself. Pay a family member or friend if they catch you smoking. The amount should be large enough ($5 - $20) to be a deterrent, but not so large as to be ridiculous. Even better -- donate the money to charity.
- If your partner or friend smokes, try persuading them to quit or, at the very least, not to smoke around you.
Studies continue to show that smokers who exercise can greatly increase their ability to quit smoking and reduce their risk for weight gain. Move the muscles when cravings occur. Dance, run, walk, jump up and down, stretch, or do push-ups. Yoga is an excellent exercise program for quitting. Older people and anyone with health problems should consult their health care provider before starting such a program.
Maintain a Healthy Diet
- Eat plenty of fresh, crunchy fruits and vegetables. This is also a useful way of satisfying oral cravings without adding many calories.
- Drink plenty of water and healthy beverages.
- Drink coffee or tea in moderation, which may help prevent weight gain, and may also have antidepressant properties. Avoid caffeine in the evening, however, since sleep disturbances can be a problem during withdrawal.
Change Daily Habits
- Change your daily schedule, particularly eating times, as much as possible. Eat at different times or eat many small meals instead of three large ones. Sit in a different chair or even a different room.
- If you smoke after eating, find other ways to end a meal. Play a tape or CD, eat a piece of fruit, get up and make a phone call, or take a walk (a good distraction that burns calories as well). For example, if you normally have a cigarette with coffee, drink tea instead or use a different cup.
- Substitute oral habits by eating celery, chewing sugarless gum, or sucking on a cinnamon stick.
- Go to public places and restaurants where smoking is prohibited or restricted.
- Set short-term quitting goals and reward yourself when you meet them.
- Every day put the money you'd normally spend on cigarettes in a jar and buy something pleasurable at the end of a predetermined period of time.
- Find activities that focus the hands and mind but are not taxing or fattening, such as playing computer games or solitaire, knitting, sewing, or doing crossword puzzles.
About 4% of smokers who quit without any outside help succeed. Nevertheless, most people try to quit alone, and many have reported that certain activities can help the process of withdrawal. The primary obstacle in trying to quit alone is making the behavioral changes needed to eliminate the habits associated with smoking. Excellent books, CDs, and manuals are available and are strongly recommended to help people who want to quit without other assistance.
Smokers who use outside help have the best record for quitting, with success rates of 25% - 35%. Those who are counseled in addition to using nicotine replacement and Zyban have the best chance of quitting. Varenicline can double or triple your odds of quitting. Brochures, CDs, and other self-help materials are often ineffective when used alone, but they may be helpful in conjunction with a counseling program.
Types of Behavioral Approaches
Problem Solving or Coping Strategies. Smokers are more likely to quit smoking when they learn thinking (cognitive) and behavioral techniques, stress management techniques, and ways to handle the symptoms of withdrawal and the urge to relapse. The more intense the counseling program, the better. Smokers should look for programs that offer the following:
- Session lengths of 20 - 30 minutes
- Four to seven sessions
- A 2-week program
- An additional 2 weeks or more of follow-up contact
The Staged Approach. The intent of the staged approach is to plan quitting interventions that are customized for each individual rather than imposing some general method for quitting. The approach takes the smoker through six stages with behavioral interventions at each point:
Most studies of this approach have been weak. Better research is needed on its benefits.
People who follow this approach do not proceed from one stage to another in a simple, step-by-step fashion. They actually cycle or spiral back and forth, so that they may move from stage 1 to 2 to 3, and then back to 2 again. They may stay in maintenance mode for years and then fall back to stage 2. Remember that this is normal -- if you tried quitting in the past and didn't stick with it, don't consider yourself a failure. Just try again.
Stage 1: Pre-Contemplation.
People at this stage have no plans or desire to stop smoking. They aren't even considering quitting. People at this stage are generally unaware of the specific benefits that quitting can bring. Or, they may have "failed" in the past and have given up. There's no point in talking about how to start a cessation program at this stage. Instead, it is important to think about how quitting will help you feel better, have more confidence, or live longer. You must identify the benefits before you will consider quitting. If you are at this stage, a good activity is to ask several friends or family members why they quit.
Stage 2: Contemplation.
A person at this stage is thinking, "I think I should probably quit, but I need help getting started." People at this stage know that quitting is good for them, but it seems like a daunting task or they don't think they can pull it off. Some may have tried and failed in the past. It's important for people at this stage to consider some of the truths and falsehoods of quitting. If you are at this stage, write down (brainstorm) all your potential roadblocks -- the things that you believe make quitting difficult -- and learn strategies for overcoming or side-stepping those hurdles. People at this stage might benefit from making a pledge, contract, or other commitment that they are going to get more active in the near future. The goal is to identify the roadblocks and ways to overcome these hurdles, and make a commitment to quitting.
Stage 3: Preparation.
Smokers at this stage are ready to quit. The goal at this stage is to create a specific action plan that takes all factors into account, so that quitting is successful. People at this stage need to know what methods work and what support exists to help them. If you are at this stage, you should consider some backup plans -- what to do when the urge to smoke hits you.
Stage 4: Action!
People at this stage have just quit. This stage is where the most behavioral change occurs. It requires significant commitment and energy. If you are at this stage, keep talking to friends and family for inspiration. Review your backup plans. Reward yourself for small achievements. Having a fellow smoker quit with you can be a huge support as you both get through this stage.
Stage 5: Maintenance.
People at this stage have been smoke-free for at least 6 months. The goal now is to prevent a relapse. If you are at this stage, continue to be wary of roadblocks and keep reminding yourself of the benefits you have gained. Think about what you have found most enjoyable about being smoke-free.
Alternative Methods for Quitting
Hypnosis. Although rigorous studies are lacking, some people report successful smoking cessation when they receive hypnosis in individual sessions. Hypnosis is effective only if you trust the therapist and can feel completely at ease in the vulnerable and passive state necessary for hypnotic suggestion.
During a typical session, the hypnotherapist will use various techniques (such as imagery and silent counting) to put you in a relaxed state.
When you are very relaxed, but not asleep, the hypnotherapist will quietly suggest motivations for not smoking. The hypnotherapist should also reinforce a positive self-image while you are in deep relaxation. This helps many people avoid the depression that accompanies withdrawal.
The sessions usually take about 1 hour.
You should be taught methods of self-hypnosis to use at home, and follow-up once to reinforce what you've learned.
Acupuncture and Acupressure. There is no real evidence that acupuncture helps people quit smoking, although this method is safe to try. The acupuncture technique for quitting smoking usually uses very tiny curved staples inserted into three different points around the edge of the ear. The procedure is painless. You will be told to press each staple in a certain order for a few seconds whenever you crave a cigarette. The acupuncturist may also use acupuncture points elsewhere on the body. There are no side effects, except for some soreness if the acupuncture staple is pressed too hard.
A related technique called acupressure involves simply pressing select points on the body when a craving hits. Some studies have reported good quit rates with acupuncture, but few rigorous studies have been conducted using acupressure.
Public Health Efforts and Social Pressure (Denormalization)
Denormalization is the idea that smoking is no longer normal. This concept is best instituted by:
- Creating laws and local regulations that make smoking inaccessible in public places
- Raising prices
- Putting stricter limitations on cigarette advertising
Increasing taxes on cigarettes may be one of the most important methods for reducing smoking in the general population, particularly in younger people.
Evidence suggests that banning smoking in work and public places may lead to a higher quit rate than in places where smoking is permitted.
Denormalization can also work on a personal level. A British study showed that in couples where one person continues to smoke, the other person usually continues to smoke too.
Symptoms of Withdrawal
After you quit smoking, you will have some withdrawal symptoms. Such symptoms generally peak in intensity 3 -5 days after you quit, and usually disappear after 2 weeks, although some may persist for several months.
The symptoms of withdrawal are both physical and mental.
- Tingling in the hands and feet
- Intestinal disorders (cramps, nausea)
- Sore throat, coughing, and signs of a cold
Withdrawal symptoms should be treated just like physical symptoms due to an illness or disease.
Mental and Emotional Symptoms. Tension and cravings build up during periods of withdrawal, sometimes to a nearly intolerable point. Nearly every moderate-to-heavy smoker experiences more than one of the following strong emotional and mental responses to withdrawal:
- Temper tantrums, intense needs, feelings of dependency, and a state of near paralysis
- Mental confusion, vagueness, or difficulty concentrating
- Irritability, restlessness, impatience, or anger
The first signs of nicotine withdrawal can appear within 30 minutes of a smoker's last cigarette. Within 3 hours, the person may experience anxiety, sadness, and difficulty concentrating.
Depression is common during withdrawal and over the long term. In the short term, it may mimic the feelings of grief felt when a loved one is lost. A smoker should plan on a period of actual mourning in order to get through the early withdrawal depression.
There is a significant association between cigarette smoking and a susceptibility to depression. People who are prone to depression have a 25% chance of becoming depressed when they quit smoking, and this increased risk persists for at least 6 months. What's more, depressed smokers have a very low level of success. Only about 6% remain smoke-free after a year. There are strong reasons for this:
- Smoking may mask depression, which can become severe even after the early stages of withdrawal have passed.
- For some smokers, the future physical damage incurred by smoking is an abstraction, which fails to motivate quitting when measured up against the very real emotional pain triggered by nicotine withdrawal.
- Not only does the smoker suffer, but the negative emotions often harm relationships with friends and family, who might even urge the ex-smoker to take up cigarettes again.
People who have depression while quitting might do better using a combination of emotionally supportive therapy (as opposed to behavioral therapy), nicotine replacements, and antidepressants, such as bupropion (Zyban). If severe depression lasts beyond the withdrawal period, seek professional help as soon as possible.
Quitting smoking does increase the risk for weight gain. Smokers who quit gain an average of 11 pounds by the end of their first year, and an extra 6 - 7 pounds in the next 4 years. However, fear of weight gain shouldn't stop people from quitting smoking. Instead, they should use weight-control measures after quitting.
Smoking uses up calories -- about 200 calories a day. Burning calories helps you lose weight. After quitting smoking, the body's metabolism slows down and food is digested better. Insulin levels increase, enabling the body to process more sugar for energy. When you quit smoking, you may snack more frequently.
How to Keep the Weight Off After Smoking. Exercise is very helpful in controlling weight. To burn the same amount of calories as you did while smoking, you need to only take an extra 15-minute daily walk and eliminate 100 calories a day from meals. Just a moderate increase in physical activity can help keep weight gain to a minimum.
Nicotine replacement therapy can also help protect against weight gain.
In people who are worried about gaining weight after they quit smoking, combining behavioral therapy for smoking-related weight concerns with the antidepressant bupropion can help them stop smoking for longer.
[See the Quitting Smoking section in this report.]
Failure to Quit
Biological, psychological, behavioral, and cultural factors all play a role in nicotine addiction, making smoking one of the hardest addictions to beat. About half of people who quit return to smoking. Even after years of not smoking, some ex-smokers still have occasional cravings for cigarettes.
Some experts suggest that, in addition to depression, there are three major areas responsible for the inability to quit:
- Mental performance. Nicotine improves concentration and thinking. Quitting smoking temporarily impairs one's mental performance.
- Stress. Although smoking many not reduce stress, stopping certainly increases it.
- Weight gain. Quitting smoking can cause you to gain weight. Studies are mixed on whether weight gain is permanent in most smokers. Weight gain is a major factor in smoking relapse. [See Weight Gain section in this report.]
How well people do in the first 2 weeks of smoking cessation is critical to their success. Smokers should not be shy about seeking all the help they can during this period. Although withdrawal symptoms can be intense, treatments are available to reduce them.
Attempts to quit are never a waste of time, since the amount of smoking is reduced during these periods. People who keep trying still have a 50 - 50 chance of finally quitting.
Individual Risk Factors for Failure
Researchers have been trying to discover individual risk factors or sets of behaviors that can help predict why specific people fail to quit. Some factors include:
- Being female
- Being a heavy smoker
- Inhaling deeply
- Being a long-term smoker
- Having severe withdrawal symptoms
Among many studies, however, only one found a single consistent factor for failure to quit: Cheating during the first 2 weeks of withdrawal, even with the patch, nearly guarantees that a person will smoke again in 6 months.
Women and Smoking
Studies show that women have a harder time trying to quit smoking and have less success with abstinence programs than men. There are many proposed reasons for this:
- Nicotine has different effects on mood in women compared to men. Women who quit may have greater anxiety and stress than men who quit.
- Women are not as physically dependent on nicotine as men, but they are more addicted to the actual behavior of smoking, which is the more powerful deterrent to quitting. This may be the reason why nicotine replacement, which only reduces cravings, tends not to be as effective in women.
- Women may fear weight gain after quitting more than men.
- Certain phases in the menstrual cycle may reduce the response to drugs that are used to help women quit smoking.
- Men may be less supportive than women in helping their partners quit.
- Women trying to quit may miss the feeling of control associated with smoking more than men.
On the positive side, evidence suggests that when women quit, their lung function seems to improve more rapidly than in men who quit.
Smokers and former smokers should immediately begin to implement a healthier lifestyle and change any other behaviors that might be damaging their health.
Everyone should maintain a healthy diet, with foods rich in whole grains and fruits and vegetables (particularly dark colored ones). Avoid saturated fats and instead choose monounsaturated fats, which are found in olive oil, or fats from oily fish. Eating fish more than twice a week might help limit the tobacco damage in people who do not smoke more than a pack-and-a-half a day.
Vitamins and Supplements
Women who are pregnant and continue to smoke must be sure to take appropriate vitamins, particularly folic acid. In this way, they might reduce the increased risk of fetal injury and death, although they will not eliminate the risk.
Regular exercise reduces a smoker's risk of heart disease (although still not to the level of a nonsmoker). Exercise does not lower a smoker's risk for lung cancer or emphysema.
If you smoke, you should be screened for any smoking-related disorders. Have your cholesterol and blood pressure checked regularly. Women should have regular Pap smears to detect cervical cancer (the required frequency of the Pap smear varies by age and medical history, such as exposure to the human papillomavirus). All older adults should be screened for colon cancer.
A note about computed tomography: Computed tomography (CT) screening programs are becoming increasingly available. These programs may claim that they can successfully detect lung cancer early. However, to date, these programs are experimental at best, and in controlled studies they offer no survival benefits for lung cancer patients.
Boffetta P, Hecht S, Gray N, et al. Smokeless tobacco and cancer. Lancet Oncol. 2008;9(7):667-675.
Boffetta P, Straif K. Use of smokeless tobacco and risk of myocardial infarction and stroke: systematic review with meta-analysis. BMJ. 2009;339:b3060.
Botteri E, Iodice S, Bagnardi V, et al. Smoking and colorectal cancer: a meta-analysis. JAMA. 2008;300(23):2765-2778.
Brion MJ,Victoria C, Matijasevich A, Horta B, Anselmi L, Steer C, et al. Maternal smoking and child psychological problems: disentangling causal and noncausal effects. Pediatrics. 2010;126(1):e57-e65.
Burke MV, Ebbert JO, Hays JT. Treatment of tobacco dependence. Mayo Clin Proc. 2008;83(4):479-483.
Centers for Disease Control and Prevention (CDC). Cigarette Smoking Among Adults -- United States, 2007. MMWR. 2008;57(45):1221-1226.
Centers for Disease Control and Prevention (CDC). Cigarette use among high school students -- United States, 1991 - 2009. MMWR. 2010;59(26):797-801.
Centers for Disease Control and Prevention (CDC). State Smoking Restrictions for Private-Sector Worksites, Restaurants, and Bars -- United States, 2004 and 2007. MMWR. 2008;57(20);549-552.
Centers for Disease Control and Prevention (CDC). National Health Interview Survey -- 2008: Early Release. 8/2009. Available online.
Centers for Disease Control and Prevention (CDC). Vital signs: Cigarette smoking among adults aged > or = 18 years -- United States, 2009. MMWR. 2010;59(Early Release):1-6.
Centers for Disease Control and Prevention (CDC). Vital signs: Nonsmokers' exposure to secondhand smoke -- United States, 1999-2008. MMWR. 2010;59(Early Release):7-12.
Chandler MA, Rennard SI. Smoking cessation. Chest. 2010;137(2):428-435.
Eisenberg MJ, Filion KB, Yavin D, et al. Pharmacotherapies for smoking cessation: a meta-analysis of randomized controlled trials. CMAJ. 2008;179(2):135-144. Erratum in: CMAJ. 2008;179(8):802.
Hays JT, Ebbert JO. Varenicline for tobacco dependence. N Engl J Med. 2008;359(19):2018-24.
Infante M, Cavuto S, Lutman FR, et al. A randomized study of lung cancer screening with spiral computed tomography: three-year results from the DANTE trial. Am J Respir Crit Care Med. 2009;180(5):445-453.
Klein R, Cruickshanks KJ, Nash SD, Krantz EM, Javier Nieto F, Huang GH, et al. The prevalence of age-related macular degeneration and associated risk factors. Arch Ophthalmol. 2010;128(6):750-758.
Ladeiras-Lopes R, Pereira AK, Nogueira A, ey al. Smoking and gastric cancer: systematic review and meta-analysis of cohort studies.. Cancer Causes Control. 2008;19(7):689-701.
Levine D. Bupriopion and cognitive behavioral therapy for weight-concerned women smokers. Arch Intern Med. 2010;170(6):543-550.
Lindson N, Aveyard P, Hughes JR. Reduction versus abrupt cessation in smokers who want to quit. Cochrane Database Syst Rev. 2010: Mar 17;3:CD008033.
Meyers DG, Neuberger JS, He J. Cardiovascular effect of bans on smoking in public places: a systematic review and meta-analysis. J Am Coll Cardiol. 2009;54(14):1249-1255.
Piper ME, Smith SS, Schlam TR, Fiore MC, Jorenby DE, Fraser D, Baker TB. A randomized placebo-controlled clinical trial of 5 smoking cessation pharmacotherapies. Arch Gen Psychiatry. 2009;66(11):1253-1262.
Pratt LA, Brody DJ. Depression and smoking in the U.S. household population age 20 and over, 2005-2008. NCHS Data Brief No. 34, published online April 14, 2010.
Riala K, Hakko H, Rasanen P; Study-70 Workgroup. Nicotine dependence is associated with suicide attempts and self-mutilation among adolescent females. Compr Psychiatry. 2009;50(4):293-298.
Rodriguez J, Jiang R, Johnson WC, MacKenzie BA, Smith LJ, Barr RG. The association of pipe and cigar use with cotinine levels, lung function, and airway obstruction: a cross-sectional study. Ann Intern Med. 2010;152(4):201-210.
Shaw GM, Carmichael SL, Vollset SE, et al. Mid-pregnancy cotinine and risks of orofacial clefts and neural tube defects. J Pediatr. 2009;154(1):17-9
U.S. Food and Drug Administration. Information for Healthcare Professionals: Varenicline (marketed as Chantix) and Bupropion (marketed as Zyban, Wellbutrin, and generics). FDA ALERT [7/1/2009]. Available online.
U.S. Preventive Services Task Force. Counseling and interventions to prevent tobacco use and tobacco-caused disease in adults and pregnant women: U.S. Preventive Services Task Force reaffirmation recommendation statement. Arch Intern Med. 2009;150(8):551-555.
Winickoff JP, Van Cleave J, Oreskovic NM. Tobacco smoke exposure and chronic conditions of childhood. Pediatrics. 2010;126(1):e251-e252.
Reviewed by: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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