National Institute on Drug Abuse
Research Report Series

Nicotine Addiction

[Nicotine Addiction Report Index] How does Nicotine Work? >>

What is nicotine?

Nicotine, one of more than 4,000 chemicals found in the smoke from tobacco products such as cigarettes, cigars, and pipes, is the primary component in tobacco that acts on the brain. Smokeless tobacco products such as snuff and chewing tobacco also contain many toxins as well as high levels of nicotine. Nicotine, recognized as one of the most frequently used addictive drugs, is a naturally occurring colorless liquid that turns brown when burned and acquires the odor of tobacco when exposed to air. There are many species of tobacco plants; the tabacum species serves as the major source of tobacco products today. Since nicotine was first identified in the early 1800s, it has been studied extensively and shown to have a number of complex and sometimes unpredictable effects on the brain and the body.

Cigarette smoking is the most prevalent form of nicotine addiction in the United States. Most cigarettes in the U.S. market today contain 10 milligrams (mg) or more of nicotine. Through inhaling smoke, the average smoker takes in 1 to 2 mg nicotine per cigarette. There have been substantial increases in the sale and consumption of smokeless tobacco products also, and more recently, in cigar sales.

Nicotine is absorbed through the skin and mucosal lining of the mouth and nose or by inhalation in the lungs. Depending on how tobacco is taken, nicotine can reach peak levels in the bloodstream and brain rapidly. Cigarette smoking, for example, results in rapid distribution of nicotine throughout the body, reaching the brain within 10 seconds of inhalation. Cigar and pipe smokers, on the other hand, typically do not inhale the smoke, so nicotine is absorbed more slowly through the mucosal membranes of their mouths. Nicotine from smokeless tobacco also is absorbed through the mucosal membranes.

Is nicotine addictive?

Yes, nicotine is addictive. Most smokers use tobacco regularly because they are addicted to nicotine. Addiction is characterized by compulsive drug-seeking and use, even in the face of negative health consequences, and tobacco use certainly fits the description. It is well documented that most smokers identify tobacco as harmful and express a desire to reduce or stop using it, and nearly 35 million of them make a serious attempt to quit each year. Unfortunately, less than 7 percent of those who try to quit on their own achieve more than 1 year of abstinence; most relapse within a few days of attempting to quit.

Other factors to consider besides nicotine's addictive properties include its high level of availability, the small number of legal and social consequences of tobacco use, and the sophisticated marketing and advertising methods used by tobacco companies. These factors, combined with nicotine's addictive properties, often serve as determinants for first use and, ultimately, addiction.

Recent research has shown in fine detail how nicotine acts on the brain to produce a number of behavioral effects. Of primary importance to its addictive nature are findings that nicotine activates the brain circuitry that regulates feelings of pleasure, the so-called reward pathways. A key brain chemical involved in mediating the desire to consume drugs is the neurotransmitter dopamine, and research has shown that nicotine increases the levels of dopamine in the reward circuits. Nicotine's pharmacokinetic properties have been found also to enhance its abuse potential. Cigarette smoking produces a rapid distribution of nicotine to the brain, with drug levels peaking within 10 seconds of inhalation. The acute effects of nicotine dissipate in a few minutes, causing the smoker to continue dosing frequently throughout the day to maintain the drug's pleasurable effects and prevent withdrawal.

What people frequently do not realize is that the cigarette is a very efficient and highly engineered drug-delivery system. By inhaling, the smoker can get nicotine to the brain very rapidly with every puff. A typical smoker will take 10 puffs on a cigarette over a period of 5 minutes that the cigarette is lit. Thus, a person who smokes about 1-1/2 packs (30 cigarettes) daily, gets 300 "hits" of nicotine to the brain each day. These factors contribute considerably to nicotine's highly addictive nature.

Scientific research is also beginning to show that nicotine may not be the only psychoactive ingredient in tobacco. Using advanced neuroimaging technology, scientists can see the dramatic effect of cigarette smoking on the brain and are finding a marked decrease in the levels of monoamineoxidase (MAO), an important enzyme that is responsible for breaking down dopamine. The change in MAO must be caused by some tobacco smoke ingredient other than nicotine, since we know that nicotine itself does not dramatically alter MAO levels. The decrease in two forms of MAO, A and B, then results in higher dopamine levels and may be another reason that smokers continue to smoke - to sustain the high dopamine levels that result in the desire for repeated drug use.

What is the extent and
impact of tobacco use?

According to the 1996 National Household Survey on Drug Abuse, an estimated 62 million Americans were current smokers in 1996, and another 6.8 million used smokeless tobacco, which means that nicotine is one of the most widely abused substances. In addition, it is estimated that each day in the United States, nearly 3,000 people under the age of 18 will start smoking. According to the Centers for Disease Control and Prevention (CDC), the prevalence of cigarette smoking among U.S. high school students increased from 27.5 percent in 1991 to 36.4 percent in 1997. NIDA's own Monitoring the Future Study, which annually surveys drug use and related attitudes of America's adolescents, also found the prevalence rates for smoking among youth remained high. Since 1975, nicotine in the form of cigarettes has consistently been the substance the greatest number of high school students use daily.

The impact of nicotine addiction in terms of morbidity, mortality, and economic costs to society is staggering. Tobacco kills more than 430,000 U.S. citizens each year - more than alcohol, cocaine, heroin, homicide, suicide, car accidents, fire, and AIDS combined. Tobacco use is the leading preventable cause of death in the United States.

Economically, smoking is responsible for approximately 7 percent of total U.S. health care costs, an estimated $50 billion each year. However, this cost is well below the total cost to society because it does not include burn care from smoking-related fires, perinatal care for low-birth-weight infants of mothers who smoke, and medical care costs associated with disease caused by secondhand smoke. Taken together, the direct and indirect costs of smoking are estimated at more than $100 billion per year.

[Nicotine Addiction Report Index] How does Nicotine Work? >>