Nicotine dependence

Nicotine dependence is a state of substance dependence on nicotine. It is a chronic, relapsing disease characterized by a compulsive craving to use the drug despite social consequences, loss of control over drug intake, and the emergence of withdrawal symptoms. Tolerance is another component of drug dependence. Nicotine dependence develops over time as an individual continues to use nicotine. While cigarettes are the most commonly used tobacco product, all forms of tobacco use—including smokeless tobacco and e-cigarette use—can cause dependence. Nicotine dependence is a serious public health problem because it leads to continued tobacco use and the associated negative health effects. Tobacco use is one of the leading preventable causes of death worldwide, causing more than 8 million deaths per year and killing half of its users who do not quit. Current smokers are estimated to die an average of 10 years earlier than non-smokers.

According to the World Health Organization, "Greater nicotine dependence has been shown to be associated with lower motivation to quit, difficulty in trying to quit, and failure to quit, as well as with smoking the first cigarette earlier in the day and smoking more cigarettes per day." The WHO estimates that there were 1.24 billion tobacco users globally in 2022^[update], with the number projected to decline to 1.20 billion in 2025. Of the 34 million smokers in the United States in 2018, 74.6% smoked every day, indicating the potential for some level of nicotine dependence. There is an increased incidence of nicotine dependence in individuals with psychiatric disorders, such as anxiety disorders and substance use disorders.

Various methods exist for measuring nicotine dependence. Common assessment scales for cigarette smokers include the Fagerström Test for Nicotine Dependence, the Diagnostic and Statistical Manual of Mental Disorders criteria, the Cigarette Dependence Scale, the Nicotine Dependence Syndrome Scale, and the Wisconsin Inventory of Smoking Dependence Motives.

Nicotine is a parasympathomimetic stimulant that binds to nicotinic acetylcholine receptors in the brain. Neuroplasticity within the brain's reward system, including an increase in the number of nicotine receptors, occurs as a result of long-term nicotine use and leads to nicotine dependence. In contrast, the effect of nicotine on human brain structure (e.g., gray matter and white matter) is less clear. Genetic risk factors contribute to the development of dependence. For instance, genetic markers for specific types of nicotinic receptors (the α5–α3–β4 nicotinic receptors) have been linked to an increased risk of dependence. Evidence-based treatments—including medications such as nicotine replacement therapy, bupropion, varenicline, or cytisine, and behavioral counseling—can double or triple a smoker's chances of successfully quitting.

Nicotine dependence is defined as a neurobiological adaptation to repeated drug exposure that is manifested by highly controlled or compulsive use, the development of tolerance, experiencing withdrawal symptoms upon cessation including cravings, and an inability to quit despite harmful effects. Nicotine dependence has also been conceptualized as a chronic, relapsing disease. A 1988 Surgeon General report states, "Tolerance" is another aspect of drug addiction [dependence] whereby a given dose of a drug produces less effect or increasing doses are required to achieve a specified intensity of response. Physical dependence on the drug can also occur, and is characterized by a withdrawal syndrome that usually accompanies drug abstinence. After cessation of drug use, there is a strong tendency to relapse."

Nicotine dependence leads to heavy smoking and causes severe withdrawal symptoms and relapse back to smoking. Nicotine dependence develops over time as a person continues to use nicotine. Teenagers do not have to be daily or long-term smokers to show withdrawal symptoms. Relapse should not frustrate the nicotine user from trying to quit again. A 2015 review found "Avoiding withdrawal symptoms is one of the causes of continued smoking or relapses during attempts at cessation, and the severity and duration of nicotine withdrawal symptoms predict relapse." Symptoms of nicotine dependence include irritability, anger, impatience, and problems in concentrating.

There are different ways of measuring nicotine dependence. The five common dependence assessment scales are the Fagerström Test for Nicotine Dependence, the Diagnostic and Statistical Manual of Mental Disorders, the Cigarette Dependence Scale, the Nicotine Dependence Syndrome Scale, and the Wisconsin Inventory of Smoking Dependence Motives.

The Fagerström Test for Nicotine Dependence focuses on measuring physical dependence which is defined "as a state produced by chronic drug administration, which is revealed by the occurrence of signs of physiological dysfunction when the drug is withdrawn; further, this dysfunction can be reversed by the administration of drug". The long use of Fagerström Test for Nicotine Dependence is supported by the existence of significant preexisting research, and its conciseness.