Nicotine is a stimulant found in certain plants, most notably tobacco. It is one of more than 4,000 chemicals found in tobacco products and the primary component that acts on the brain. Nicotine is one of the most heavily used addictive drugs in the U.S., and smoking tobacco is the leading preventable cause of disease, disability, and death. Cigarette smoking accounts for 90 percent of lung cancer cases in the U.S., and about 40,000 deaths per year can be attributed to secondhand smoke. Most cigarettes sold in the U.S. today contain 10 milligrams or more of nicotine.
In 1989, the Surgeon General issued a report indicating that cigarettes and other forms of tobacco that contain nicotine (such as cigars, pipe tobacco, and chewing tobacco) are addictive. The report also determined that smoking was a major cause of stroke. Most smokers know that tobacco is harmful and express a desire to decrease or end use of it, with nearly 35 million people seriously attempting to quit each year. Unfortunately, most relapse within just a few days, and less than seven percent of those who try to quit on their own achieve a year of abstinence.
Besides nicotine's addictive properties, other factors that lead to its widespread use include its wide availability, the small number of legal and social consequences of tobacco use, and the sophisticated marketing and advertising methods of tobacco companies.
Symptoms of Use
Nicotine is highly addictive. The ingestion of nicotine results in a discharge of epinephrine from the adrenal cortex, causing a sudden release of glucose. Stimulation is followed by depression and fatigue, leading the user to seek more nicotine.
The medical consequences of nicotine exposure result from the effects of both the nicotine itself and how it is taken. In addition to nicotine, cigarette smoke is primarily composed of gases (mainly carbon monoxide) and tar. The tar in a cigarette leads to a high risk of emphysema, lung cancer, and bronchial disorders. The carbon monoxide in the smoke increases the chance of cardiovascular diseases.
Nicotine exposure has also been linked to the following:
- Lung diseases such as chronic bronchitis and emphysema
- Exacerbation of asthma symptoms
- Associations with cancers of mouth, kidney, esophagus, pharynx, larynx, stomach, pancreas, cervix, ureter, and bladder
- Increased risk of heart disease including stroke, vascular disease, heart attack, and aneurysm
- Earlier menopause in female smokers
- Increased risk of cardiovascular and cerebrovascular diseases in female smokers who take oral contraceptives
- Increased risk, for pregnant smokers, of stillborn, premature, or low-birth weight infants
- Increased risk for developing conduct disorders in children whose mothers smoked while pregnant
- Passive or secondary smoke increases risk for many diseases including lung cancer and cardiovascular disease in nonsmokers, as well as increasing the severity of asthma in children and the incidence of sudden infant death syndrome
Tobacco Use Disorder
Tobacco Use Disorder refers to a pattern of tobacco use that leads to clinically significant impairment or distress within a 12-month period. It is common among people who use cigarettes and smokeless tobacco daily and is not common among people who do not use tobacco daily or who use nicotine medications.
In order to be diagnosed with Tobacco Use Disorder, two of the following symptoms must be identified:
- Tobacco is taken in larger dosages and/or for a longer period of time than intended
- There is a persistent desire and/or failed attempts to reduce tobacco use
- A large amount of time goes into the procuring or using tobacco
- An overwhelming desire or urge to use tobacco
- The inability, due to tobacco use, to maintain obligations for one's job, school, or home life
- Continued tobacco use in the face of social/interpersonal problems that result from, or are made worse by, the use of the stimulant
- Tobacco use becomes prioritized to such an extent that social, occupational, and recreational activities are either given up on completely or are reduced drastically
- Tobacco use occurs even in situations where it becomes physically hazardous
- Use of tobacco continues even though one knows the physical and psychological risks and problems associated with it
- A considerable increase in the amount of tobacco is needed to achieve the desired effect, or the same amount of tobacco no longer produces the desired effect
- Withdrawal symptoms characteristic of tobacco use are present, or tobacco is taken to relieve or avoid withdrawal symptoms
Cessation of nicotine use is followed by a withdrawal period that may last a month or more and includes symptoms that can quickly drive people back to use. Nicotine withdrawal symptoms may begin within a few hours after use, and include:
- sleep disturbances
- cognitive and attentional deficits
- increased appetite
Symptoms generally peak within the first few days and may subside within a few weeks, though for some people, they may persist for months or longer.
An important and poorly understood component of nicotine withdrawal is craving, or a continued urge to use nicotine. Craving has been described as a major obstacle to successful abstinence and may persist for six months or longer. While the withdrawal itself is related to the pharmacological effects of nicotine, the severity of withdrawal symptoms can also be affected by psychological experiences. For some people, the feel, smell, and sight of a cigarette and the ritual of obtaining, handling, lighting, and smoking it are all associated with the pleasurable effects of smoking and can make withdrawal or craving worse. While nicotine gum and patches may alleviate the pharmacological aspects of withdrawal, cravings often persist.
Nicotine is absorbed through the skin and mucosal lining of the nose and mouth or in the lungs (through inhalation). Nicotine can reach peak levels in the bloodstream and brain rapidly; cigarette smoking results in nicotine reaching the brain within just 10 seconds of inhalation. The acute effects of nicotine dissipate within a few minutes, causing the need to continue repeated intake throughout the day.
Nicotine acts as both a stimulant and a sedative. Immediately after exposure to nicotine, there is a "kick" caused in part by the drug's stimulation of the adrenal glands and resulting discharge of epinephrine (adrenaline). The rush of adrenaline stimulates the body, causing a sudden release of glucose as well as an increase in blood pressure, heart rate, and respiration. Nicotine also suppresses insulin output from the pancreas, causing smokers to be slightly hyperglycemic. In addition, nicotine indirectly causes a release of dopamine in the brain regions that control pleasure and motivation. This reaction is similar to that seen with other abused drugs—such as cocaine and heroin—and is thought to underlie the pleasurable sensations many smokers experience. In contrast, nicotine can also exert a sedative effect, depending on the level of the smoker's nervous system arousal and the dose of nicotine taken.
Repeated exposure to nicotine results in the development of tolerance, the condition in which higher doses of a drug are required to produce the same initial effect. Nicotine is metabolized fairly rapidly, disappearing from the body in a few hours. Some tolerance is lost overnight; it progresses as the day develops, and later cigarettes have less effect.
Due to nicotine's addictive nature, smoking can easily become a habit. An individual may develop a routine surrounding the act of smoking, for example, smoking after every meal or in certain locations or under certain levels of stress. If someone is to overcome the addiction to nicotine, they will likely have to change the behaviors they associate with smoking.
Research has shown that nicotine may not be the only psychoactive ingredient in tobacco. 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 enzyme responsible for breaking down dopamine. The change in MAO must be caused by some tobacco smoke ingredient other than nicotine, since nicotine itself does not dramatically alter MAO levels. The need to sustain the high dopamine levels results in the desire for repeated drug use.
Research suggests that a person should quit smoking gradually to lessen the severity of withdrawal symptoms. Rates of relapse are highest in the first few weeks and months and diminish considerably after three months.
Studies have shown that pharmacological treatment combined with psychological treatment (such as psychological support and skills training to get through high-risk situations) results in some of the highest long-term abstinence rates.
Smoking cessation can have a major positive impact on a person's health; for example, a 35-year-old man who quits smoking will, on average, increase his life expectancy by about five years.
Nicotine replacement therapies (NRTs), such as nicotine gum and the nicotine patch, were the first pharmacological treatments approved by the Food and Drug Administration (FDA) for use in smoking cessation therapy. NRTs deliver a controlled dose of nicotine to a smoker to relieve withdrawal symptoms during the smoking cessation process. They are most successful when used in combination with behavioral treatments. FDA-approved NRT products include nicotine chewing gum, the nicotine transdermal patch, nasal sprays, inhalers, and lozenges.
Bupropion and varenicline are two FDA-approved non-nicotine medications that effectively increase rates of long-term abstinence from smoking. Bupropion, a medication that goes by the trade name Zyban, was approved by the FDA in 1997 for use in smoking cessation. Varenicline tartrate (Chantix) targets nicotine receptors in the brain, easing withdrawal symptoms and blocking the effects of nicotine if people resume smoking.
Several other non-nicotine medications are being investigated for the treatment of tobacco addiction, including other antidepressants and antihypertensive medication. Scientists are also investigating the potential of a vaccine that targets nicotine for use in relapse prevention. Studies to date have shown that a nicotine vaccine is safe and capable of inducing the production of long-lasting antibodies that help prevent smoking relapse. By binding nicotine in the bloodstream and thereby blocking its entry into the brain, the resulting reduction of reinforcing effects is expected to prevent relapse.
Behavioral interventions can play an integral role in nicotine addiction treatment, either in conjunction with medication or by themselves. There are a variety of methods to assist smokers in quitting, ranging from self-help materials to individual cognitive-behavioral therapy. These interventions teach individuals to recognize high-risk smoking situations, develop alternative coping strategies, manage stress, improve problem-solving skills, and increase social support.
Quitting smoking can be difficult. People can be helped during the time an intervention is delivered; however, most intervention programs are short-term (one to three months). Within six months, 75-80 percent of people who try to quit smoking relapse. Research has now shown that extending treatment beyond the typical duration of a smoking cessation program can produce quit rates as high as 50 percent at one year.
Using pharmacological treatments can increase the odds of success. However, a combination of pharmacological and behavioral treatments—for example, combining the nicotine patch with group therapy—further improves chances.