Nicotine is one of the most heavily used addictive drugs in the United
States. In 2002, 30 percent of the U.S. population 12 and older—71.5 million
people—used tobacco at least once in the month prior to being interviewed. This
figure includes 3.8 million young people age 12 to 17; 14 million people age 18
to 25; and 53.7 million age 26 and older.* Most of them smoked
cigarettes.
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 more than 440,000 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).
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.
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 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 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.
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 the
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.
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 transdermal patch, a skin patch
that delivers a relatively constant amount of nicotine to the person wearing it.
A research team at NIDA’s Intramural Research Program studied the safety,
mechanism of action, and abuse liability of the patch that was consequently
approved by FDA. Both nicotine gum and the nicotine patch, as well as other
nicotine replacements such as sprays and inhalers, are used to help people fully
quit smoking by reducing withdrawal symptoms and preventing relapse while
undergoing behavioral treatment.
Another tool in treating nicotine
addiction is a medication that goes by the trade name Zyban. This is not a
nicotine replacement, as are the gum and patch. Rather, this works on other
areas of the brain, and its effectiveness is in helping to make controllable
nicotine craving or thoughts about cigarette use in people trying to
quit.
2003 Monitoring the Future Survey (MTF)**
Despite the demonstrated health risk associated with smoking, young Americans
continue to smoke. However, past-month smoking rates among high school students
are declining from peaks reached in 1996 for 8th-graders (21.0 percent) and
10th-graders (30.4 percent) and in 1997 for seniors (36.5 percent). In 2003,
rates reached the lowest levels ever reported by MTF; 10.2 percent of
8th-graders, 16.7 percent of 10th-graders, and 24.4 percent of high school
seniors reported smoking during the month preceding their responses to the
survey.
The decrease in smoking rates among young Americans corresponds
to several years in which increased proportions of teens said they believe there
is a “great” health risk associated with cigarette smoking and expressed
disapproval of “pack-a-day” smokers. Students’ personal disapproval of smoking
had risen for some years, but showed no further increase in 2003 among
8th-graders and only small increases among 10th- and 12th-graders. In 2003, 84.6
percent of 8th-graders, 81.4 percent of 10th-graders, and 74.8 percent of
12th-graders stated that they “disapprove” or “strongly disapprove” of people
smoking one or more packs of cigarettes per day.
For additional information on nicotine abuse and addiction, please visit www.smoking.drugabuse.gov.
For more information on how to quit smoking, please visit www.cdc.gov/tobacco.
* These findings are from the 2002 National Survey on Drug Use and Health,
produced by HHS’s Substance Abuse and Mental Health Services Administration. The
survey is based on interviews with 68,126 respondents who were interviewed in
their homes. The interviews represent 98 percent of the U.S. population age 12
and older. Not included in the survey are persons in the active military, in
prisons, or other institutionalized populations, or who are homeless. Findings
from the 2002 National Survey on Drug Use and Health are available online at www.DrugAbuseStatistics.samhsa.gov.
**
These data are from the 2003 Monitoring the Future Survey, funded by the
National Institute on Drug Abuse, National Institutes of Health, DHHS, and
conducted by the University of Michigan’s Institute for Social Research. The
survey has tracked 12th-graders’ illicit drug use and related attitudes since
1975; in 1991, 8th- and 10th-graders were added to the survey. The latest data
are online at www.drugabuse.gov.