Nicotine is one of the most heavily used addictive drugs in the United
States. In 2003, 29.8 percent of the U.S. population 12 and older—70.8 million
people—used tobacco at least once in the month prior to being interviewed.* This
figure includes 3.6 million young people age 12 to 17. There were no
statistically significant changes in past-month rates of the different tobacco
products among this age group between 2002 and 2003. However, there were
significant declines in past-year and lifetime cigarette use between 2002 and
2003. In addition, the rate of past-month cigarette use decreased among 13
year-olds. Young adults aged 18 to 25 reported the highest rate of current use
of any tobacco products (44.8 percent).
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.
The report also determined that smoking was a major cause of stroke and the
third leading cause of death in the United States. Statistics from the Centers
for Disease Control and Prevention indicate that tobacco use remains the leading
preventable cause of death in the United States, causing approximately 440,000
premature deaths each year and resulting in an annual cost of more than $75
billion in direct medical costs. (See www.cdc.gov/tobacco/issue.htm).
Health Hazards
Nicotine is highly addictive. Nicotine provides 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.
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.
Women who smoke generally have earlier menopause. If women
smoke cigarettes and also take oral contraceptives, they are more prone to
cardiovascular and cerebrovascular diseases than are other smokers; this is
especially true for women older than 30.
Pregnant women who smoke
cigarettes run an increased risk of having stillborn or premature infants or
infants with low birthweight. Children of women who smoked while pregnant have
an increased risk for developing conduct disorders. National studies of mothers
and daughters have also found that maternal smoking during pregnancy increased
the probability that female children would smoke and would persist in
smoking.
Adolescent smokeless tobacco users are more likely than
nonusers to become cigarette smokers. Behavioral 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 antismoking messages.
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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 an
increased risk 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 secondhand smoke causes
lung cancer in adults and greatly increases the risk of respiratory illnesses in
children and sudden infant death.
Promising Research
Research has shown that nicotine, like cocaine, heroin, and marijuana,
increases the level of the neurotransmitter dopamine, which affects the brain
pathways that control reward and pleasure. Scientists now have pinpointed a
particular molecule [the beta 2 (b2)] subunit of the nicotine cholinergic
receptor as a critical component in nicotine addiction. Mice that lack this
subunit fail to self-administer nicotine, implying that without the b2 subunit,
the mice do not experience the positive reinforcing properties of nicotine. This
new finding identifies a potential site for targeting the development of
nicotine addiction medications.
Other new research found that individuals
have greater resistance to nicotine addiction if they have a genetic variant
that decreases the function of the enzyme CYP2A6. The decrease in CYP2A6 slows
the breakdown of nicotine and protects individuals against nicotine addiction.
Understanding the role of this enzyme in nicotine addiction gives a new target
for developing more effective medications to help people stop smoking.
Medications might be developed that can inhibit the function of CYP2A6, thus
providing a new approach to preventing and treating nicotine
addiction.
Another study found dramatic changes in the brain’s pleasure
circuits during withdrawal from chronic nicotine use. These changes are
comparable in magnitude and duration to similar changes observed during
withdrawal from other abused drugs such as cocaine, opiates, amphetamines, and
alcohol. Scientists found significant decreases in the sensitivity of the brains
of laboratory rats to pleasurable stimulation after nicotine administration was
abruptly stopped. These changes lasted several days and may correspond to the
anxiety and depression experienced by humans for several days after quitting
smoking “cold turkey.” The results of this research may help in the development
of better treatments for the withdrawal symptoms that may interfere with
individuals’ attempts to quit smoking.
Treatment
Studies have shown that pharmacological treatment combined with behavioral
treatment, including psychological support and skills training to overcome
high-risk situations, results in some of the highest long-term abstinence rates.
Generally, rates of relapse for smoking cessation are highest in the first few
weeks and months and diminish considerably after about 3
months.
Behavioral economic studies find that alternative rewards and
reinforcers can reduce cigarette use. One study found that the greatest
reductions in cigarette use were achieved when smoking cost was increased in
combination with the presence of alternative recreational
activities.
Nicotine chewing gum is one medication approved by the Food
and Drug Administration (FDA) for the treatment of nicotine dependence. Nicotine
in this form acts as a nicotine replacement to help smokers quit
smoking.
The success rates for smoking cessation treatment with nicotine
chewing gum vary considerably across studies, but evidence suggests that it is a
safe means of facilitating smoking cessation if chewed according to instructions
and restricted to patients who are under medical supervision.
Another
approach to smoking cessation is the nicotine tran
