Nicotine is one of the most heavily used addictive drugs in the United States. Cigarette smoking has been the most popular method of taking nicotine since the beginning of the 20th century.
In 1989, the U.S. Surgeon General issued a report that concluded that cigarettes and other forms of tobacco, such as cigars, pipe tobacco, and chewing tobacco, are addictive and that nicotine is the drug in tobacco that causes addiction. In addition, the report determined that smoking was a major cause of stroke and the third leading cause of death in the United States.
Nicotine is highly addictive. It is both a stimulant and a sedative to the central nervous system. The ingestion of nicotine results in an almost immediate kick because it causes a discharge of epinephrine from the adrenal cortex. This stimulates the central nervous system, and other endocrine glands, which causes a sudden release of glucose. Stimulation is then followed by depression and fatigue, leading the abuser to seek more nicotine. Nicotine is absorbed readily from tobacco smoke in the lungs, and it does not matter whether the tobacco smoke is from cigarettes, cigars, or pipes.
Nicotine also is absorbed readily when tobacco is chewed. With regular use of tobacco, levels of nicotine accumulate in the body during the day and persist overnight. Thus, daily smokers or chewers are exposed to the effects of nicotine for 24 hours each day. Nicotine taken in by cigarette or cigar smoking takes only seconds to reach the brain but has a direct effect on the body for up to 30 minutes.
Research has shown that stress and anxiety affect nicotine tolerance and dependence. The stress hormone corticosterone reduces the effects of nicotine; therefore, more nicotine must be consumed to achieve the same effect. This increases tolerance to nicotine and leads to increased dependence. Studies in animals have also shown that stress can directly cause relapse to nicotine self-administration after a period of abstinence.
Addiction to nicotine results in withdrawal symptoms when a person tries to stop smoking. For example, a study found that when chronic smokers were deprived of cigarettes for 24 hours, they had increased anger, hostility, and aggression, and loss of social cooperation. Persons suffering from withdrawal also take longer to regain emotional equilibrium following stress. During periods of abstinence and/or craving, smokers have shown impairment across a wide range of psychomotor and cognitive functions, such as language comprehension.
Adolescent smokeless tobacco users are more likely than nonusers to become cigarette smokers. Behavioural research is beginning to explain how social influences, such as observing adults or other peers smoking, affect whether adolescents begin to smoke cigarettes. Research has shown that teens are generally resistant to many kinds of anti-smoking messages.
In addition to nicotine, cigarette smoke is primarily composed of a dozen gases (mainly carbon monoxide) and tar. The tar in a cigarette, which varies from about 15 mg for a regular cigarette to 7 mg in a low-tar cigarette, exposes the user to a high expectancy rate of lung cancer, emphysema, and bronchial disorders. The carbon monoxide in the smoke increases the chance of cardiovascular diseases. The Environmental Protection Agency has concluded that second hand smoke causes lung cancer in adults and greatly increases the risk of respiratory illnesses in children and sudden infant death.