In all these criteria, the central element of addiction is that the substance controls your behavior by producing temporary alterations in your mood when it is not in your system.

Smoking of Tobacco

The smoking of tobacco, in cigarettes, cigars, or a pipe, is a habit that meets many of the criteria that define an addiction. For some smokers, it provides a relief from anxiety and tension; but for others, it becomes a physical and psychological burden. Cigar and pipe smoking, although they present some hazards to health, are thought to be less dangerous to health than cigarette smoking.

Cigarette smoking damages the lungs, blood vessels, and, to a lesser extent, other organs, such as the heart.

Cancer of the lung is a serious health hazard; the peak of its incidence in men occurs in the 55 to 65 age group (when 1 in 7 deaths results from lung cancer). Approximately 2 out of every 5 heavy smokers die before the age of 65. In women who smoke, the highest mortality rate occurs 10 years earlier than in men, and 1 death in 3 caused by lung cancer will be that of a woman.

People who smoke not only damage their own health, but also harm others. For instance, a pregnant woman who smokes harms her unborn child; children exposed to smoke have more respiratory illnesses; a person who suffers from heart disease may be adversely affected by other persons' smoke; and people who live or work in smoky environments have an increased risk of developing respiratory ailments. In the last several years, many governmental agencies and private companies have instituted policies that limit or ban smoking in public areas.

Although the sale of cigarettes to persons below the age of 18 is not allowed in the United States and other countries, tobacco remains one of the most easily obtained addictive drugs.

Q:   What are the harmful substances in tobacco and what do they do?

A:   There are four main groups of dangerous substances in tobacco smoke. Nicotine is the substance that causes addiction. It stimulates the release of epinephrine and other substances in the body that cause an increase in pulse rate, a rise in blood pressure, and a narrowing of the blood vessels in the skin. Epinephrine also causes an increase in fatty substances in the blood and makes blood platelets (factors in blood clotting) stickier and therefore more likely to form blood clots.

Carbon monoxide is a poisonous gas produced by the incomplete burning of tobacco. In the lungs, it combines with hemoglobin in the blood and thus prevents the hemoglobin from carrying its full quota of oxygen throughout the circulation. It reduces a person's physical fitness and also acts as a poison.

Various substances in tobacco irritate the lining of the bronchi, inducing spasm and increasing bronchial secretions. At the same time, these irritants damage cells that usually sweep the secretions out of the lungs. This increases the likelihood of developing bronchitis.

Cancer-producing substances are present in the tar in cigarette smoke.

Q:   Is there any way of reducing the dangers of cigarette smoking?

A:   Yes. Obviously, the best way of avoiding the dangers of cigarette smoking is to give up the habit. Cigarettes, preferably with filters, should be smoked to a long stub, not a short one. Removing the cigarette from the mouth between puffs helps reduce the amount of smoke that is inhaled. Nicotine chewing gum is of moderate value as an adjunct to behavioral or psychological therapy for physically dependent smokers who wish to quit entirely. Recently transdermal continuous low-level nicotine systems have become available, allowing a replacement of part of the nicotine level obtained by smoking. These nicotine patches have been more effective than the gum. The patches are contraindicated in nonsmokers, pregnant women, and patients with a recent heart attack, life-threatening heart rhythm disturbances, or unstable angina.

Q:   What effect does smoking during pregnancy have on the fetus?

A:   Babies born to mothers who smoke are 5 to 13 ounces (140 to 364 g) lighter on average than those born to nonsmoking mothers. Also, pregnant women who smoke are more likely to have a miscarriage, stillborn baby, or infant that dies soon after birth. Twice as many premature babies are born to smoking mothers as to nonsmoking mothers. Evidence also suggests that by the age of 11 the children of mothers who smoked more than 10 cigarettes a day during pregnancy are slightly shorter and slightly below average in reading, math, and general ability than children of non-smoking mothers.

Q:   What are the effects of smoking on the lungs?

A:   Chronic bronchitis and, eventually, emphysema commonly occur in heavy smokers, and a morning cough is a common feature of all smokers. Early lung damage can be detected by pulmonary function tests before there is any obvious shortness of breath.

Among persons who smoke a pack of cigarettes a day, lung cancer occurs 20 times more frequently than in nonsmokers. The risk is increased in those who smoke high-tar cigarettes, who inhale deeply, and who began smoking in adolescence.

Q:   Can smoking cause other cancers?

A:   Yes. There are more cancers of the bladder and pancreas in smokers than in nonsmokers. Cancer of the mouth, tongue, larynx, and esophagus are also more common in smokers of all kinds of tobacco.

Q:   Can smoking affect the heart?

A:   Cigarette smoking increases the likelihood of arteriosclerosis and doubles the risk of coronary thrombosis. The risk of developing other blood vessel disorders is also increased.

Q:   What other diseases are more likely to occur in smokers?

A:   Dental and gum disorders occur more commonly in smokers. Smokers are also more likely to develop tuberculosis, probably because the damaging effect of the irritants in tobacco lowers the resistance of the lungs to this type of infection.

Although smoking does not cause peptic ulcers, the continued habit prevents them from healing. Consequently, complications are more common and mortality is greater from perforated ulcers.

Q:   What are the benefits of stopping smoking?

A:   Within a few days or weeks, there is an improvement in the sense of taste and smell, a gradual reduction in the amount of morning coughing, and less shortness of breath during exercise. There is often a temporary increase in phlegm production.

Although lung damage, such as that caused by chronic bronchitis and emphysema, cannot be reversed once it has occurred, its progress is arrested.

However, the greatest long-term benefit is the steady decrease in the chances of getting cancer. If a person who stops smoking cigarettes lives for 10 years, his or her chance of developing lung cancer is no more than for someone who has never smoked.

Smoking and Your Digestive System

From the National Institute of Diabetes and Digestive and Kidney Diseases

Cigarette smoking causes a variety of life-threatening diseases, including lung cancer, emphysema, and heart disease. An estimated 400,000 deaths each year are caused directly by cigarette smoking. Smoking is responsible for changes in all parts of the body, including the digestive system. This fact can have serious consequences because it is the digestive system that converts foods into the nutrients the body needs to live. Current estimates indicate that about one-third of all adults smoke. And, while adult men seem to be smoking less, women and teenagers of both sexes seem to be smoking more. How does smoking affect the digestive system of all these people?

Harmful Effects
Smoking has been shown to have harmful effects on all parts of the digestive system, contributing to such common disorders as heartburn and peptic ulcers. It also increases the risk of Crohn's disease and possibly gallstones. Smoking seems to affect the liver, too, by changing the way it handles drugs and alcohol. In fact, there seems to be enough evidence to stop smoking solely on the basis of digestive distress.

Heartburn
Heartburn is common among Americans. More than 60 million Americans have heartburn at least once a month, and about 15 million have it daily.

Heartburn happens when acidic juices from the stomach splash into the esophagus. Normally, a muscular valve at the lower end of the esophagus, the lower esophageal sphincter (LES), keeps the acid solution in the stomach and out of the esophagus. Smoking decreases the strength of the esophageal valve, thereby allowing stomach juice to reflux, or flow backward into the esophagus.

Smoking also seems to promote the movement of bile salts from the intestine to the stomach, which makes the stomach juice more harmful. Finally, smoking may directly injure the esophagus, making it less able to resist further damage from refluxed material.

Peptic Ulcer
A peptic ulcer is an open sore in the lining of the stomach or duodenum, the first part of the small intestine. The exact cause of ulcers is not known. A relationship between smoking cigarettes and ulcers, especially duodenal ulcers, does exist. The 1989 Surgeon General's report stated that ulcers are more likely to occur, less likely to heal, and more likely to cause death in smokers than in nonsmokers.

Why is this so? Doctors are not really sure, but smoking does seem to be one of several factors that work together to promote the formation of ulcers.

For example, some research suggests that smoking might increase a person's risk of infection with the bacterium Helicobacter pylori (H. pylori). Most peptic ulcers are caused by this bacterium.

Stomach acid is also important in producing ulcers. Normally, most of this acid is buffered by the food we eat. Most of the unbuffered acid that enters the duodenum is quickly neutralized by sodium bicarbonate, a naturally occurring alkali produced by the pancreas. Some studies show that smoking reduces the bicarbonate produced by the pancreas, interfering with the neutralization of acid in the duodenum. Other studies suggest that chronic cigarette smoking may increase the amount of acid secreted by the stomach. Whatever causes the link between smoking and ulcers, two points have been repeatedly demonstrated: People who smoke are more likely to develop an ulcer, especially a duodenal ulcer, and ulcers are less likely to heal quickly among smokers in response to otherwise effective treatment. This research tracing the relationship between smoking and ulcers strongly suggests that a person with an ulcer should stop smoking.

Liver Disease
The liver is an important organ that has many tasks. Among other things, the liver is responsible for processing drugs, alcohol, and other toxins to remove them from the body. There is evidence that smoking alters the ability of the liver to handle these substances. In some cases, this may influence the dose of medication necessary to treat an illness. Some research also suggests that smoking can aggravate the course of liver disease caused by excessive alcohol intake.

Crohn's Disease
Crohn's disease causes inflammation deep in the lining of the intestine. The disease, which causes pain and diarrhea, usually affects the small intestine, but it can occur anywhere in the digestive tract. Research shows that current and former smokers have a higher risk of developing Crohn's disease than nonsmokers do. Among people with the disease, smoking is associated with a higher rate of relapse, repeat surgery, and immunosuppressive treatment. In all areas, the risk for women, whether current or former smokers, is slightly higher than for men. Why smoking increases the risk of Crohn's disease is unknown, but some theories suggest that smoking might lower the intestine's defenses, decrease blood flow to the intestines, or cause immune system changes that result in inflammation.

Gallstones
Several studies suggest that smoking may increase the risk of developing gallstones and that the risk may be higher for women. However, research results on this topic are not consistent, and more study is needed.

Can the Damage Be Reversed?

Some of the effects of smoking on the digestive system appear to be of short duration. For example, the effect of smoking on bicarbonate production by the pancreas does not appear to last. Within a half-hour after smoking, the production of bicarbonate returns to normal. The effects of smoking on how the liver handles drugs also disappear when a person stops smoking. However, people who no longer smoke still remain at risk for Crohn's disease. Clearly, this question needs more study.