Scientists Discover a Genetic Link to Cigarette Smoking Addiction

By Mary

In a study published in the April 3, 2008 issue of the journal Nature, scientists highlighted the advances that are being made in genetics research; particularly in terms of identifying gene variants that increase the risk of bio-behavioral disorders, such as addiction to cigarette smoking. 

Researchers have been able to identify a genetic variant which

1. Makes smokers more susceptible to nicotine addiction

2. Increases the risk of developing lung cancer and peripheral arterial disease. 

This important finding revealed the variant is closely linked to two of the known subunits of nicotine receptors – the sites on the surface of many cells in the brain and body that can be bound by nicotine. Once nicotine attaches to these receptors in the brain, cell activity changes which often results in addiction to the powerful drug. 

The ground-breaking study further revealed carriers of this genetic variant are more likely than non-carriers to be heavy smokers, experience increased dependency on nicotine and are less likely to quit smoking. It is interesting to note: a person who carries the variant gene is not more likely to begin smoking; if they do start smoking, however, these individuals are much more likely to become addicted. 

The importance of reducing the number of youth who start smoking was the highlight of this study, according to researchers at the University of Utah and their colleagues at the University of Wisconsin, Madison. 

Nearly 3,000 European-American long-term smokers (recruited in Wisconsin and Utah) were studied by the Universities. The smoking habits of all participants were recorded in great detail; the age they began smoking, how many years they have smoked and the average number of cigarettes smoked each day. DNA samples were collected from all participants and researchers recorded the occurrence of the genetic variants found among this sample group.   Among the surprising findings: 

• Smokers who began the habit before the age of 17 had a nearly 2-fold to almost 5-fold increase in developing into heavy smokers as adults
• For smokers who began smoking at age 17 or later, presence of the variant gene did not significantly increase their risk for later addiction to nicotine 

Professor of Human Genetics at the University of Utah and lead author of the study, Robert Weiss PhD, explains” We know that people who begin smoking at a young age are more likely to face severe nicotine dependence later in life. This finding suggests that genetic influences expressed during adolescence contribute to the risk of a lifetime addiction severity produced from the early onset of tobacco use.” 

Dr. Nora Volkow, Director of the National Institute on Drug Abuse (NIDA) stated “In recent years we’ve seen an explosion in the understanding of how small genetic variations can impact all aspect of health, including addiction. As we learn more about how both genes and environment play a role in smoking, we will be able to better tailor both prevention and cessation programs to individuals.” 

• 8.1% of 8^th graders had used cigarettes at least once in the month prior to being surveyed
• The numbers climbed to 14.0% among 10^th graders surveyed
• Nearly 22% of 12^th graders had smoked at least once in the month prior 

Even though cigarette use has been on a slow decline in recent years, more than 3 million young people (Ages 12-17) or 13% of those in the U.S.A. still smoke. 

These findings are so exciting because identifying the genetic variant which leads smokers to addiction may also prove extremely important in understanding and combating other addictions as well.