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Nicotine Dependence
Smoking is the leading cause of preventable death, causing approximately five million premature deaths world-wide each year.
One of every six deaths in the United States can be linked to the smoking of tobacco, making this substance more lethal than all other addictive drugs combined.
Nicotine, a component of tobacco, is the primary reason for its addictiveness. However, cigarette smoke contains many other dangerous chemicals, including tar, carbon monoxide, acetaldehyde, nitrosamines, and more. The inhalation of tar increases the risk of lung cancer, emphysema, and bronchial disorders. Carbon monoxide increases the chance of developing cardiovascular diseases. Additionally, secondhand smoke increases the risk of lung cancer in adults and greatly increases the risk of respiratory illnesses in children.
So why do people smoke? Nicotine addiction is what keeps many people smoking despite its harmful effects. In general, addiction is characterized by the compulsive seeking and use of a particular stimulus, even in the face of negative health consequences. It is well documented that most smokers identify tobacco use as harmful and express a desire to reduce or stop using it. Unfortunately, only about 6 percent of people who try to quit are successful for more than a month.
Although the addictive properties of nicotine affect almost all smokers, there are also individual differences in smoking behavior, nicotine dependence, and cessation success. Some of these individual differences have been attributed to genetic factors, prompting a search for susceptibility genes. Recently scientists at deCODE genetics discovered an association between Nicotine Dependence and a specific variant in the genome. The variant is located on chromosome 15 within the nicotinic acetylcholine receptor gene cluster. The variant does not seem to influence the likelihood of whether people start to smoke or not, but among smokers, carriers of the genetic variant smoke more than non-carriers and have higher rates of nicotine dependence, making it more difficult for them to quit. In smokers, this same variant also increases the risk for Lung cancer and Peripheral arterial disease.
The deCODEme Genetic Scan identifies the risk variant rs1051730 on chromosome 15 and provides an interpretation of the associated genetic risk for nicotine dependence. Since the genetic variant has not been associated with the initiation of smoking, the associated risk applies only to those individuals who are or have been smokers.
This content was last reviewed on February 11, 2010.
