Ninety percent of lung cancer cases in America can be directly attributed to smoking. It\u2019s one of the country\u2019s foremost legal addictions\u2014you can head down to the store and load up on dangerous and addictive substances without attracting attention from the law. Tobacco addiction causes more deaths than HIV, illicit drug use, alcohol use, suicides, murders and car accidents combined, according to the Centers for Disease Control and Prevention. Despite all of these facts, people across the country continue to inhale carcinogenic cigarette fumes every day. Although most of them want to quit smoking, 85 percent of those who try fail within a week, according to the National Institute on Drug Abuse. A new study from Duke University may have revealed an important reason the relapse rate is so high among smokers. This finding doesn\u2019t offer much assistance during treatment, but could lead to a more effective approach to the prevention of nicotine addiction in the first place. Why Is Nicotine Addictive? The addictive properties of nicotine have been compared to those of heroin and cocaine\u2014which puts the dangers of tobacco into perspective. Like many drugs of abuse, nicotine stimulates \u00a0dopamine production in the brain. This is basically the brain\u2019s \u201cpleasure\u201d chemical, and nicotine is disseminated throughout the brain so quickly that it causes a rapid spike in dopamine within 10 seconds of inhalation. This sensation alone is enough to encourage addiction to many different substances, but the fact that the effects disappear quickly with nicotine makes it even riskier. Smokers need another cigarette to experience the same \u201chigh\u201d again, and then another, and another, and so on. This repeated dosing of nicotine leads to addiction. One of the easiest markers for addiction to understand and identify is withdrawal. As a result of the artificially elevated dopamine levels in the brain, it eventually reduces its own production to maintain a chemical balance. This means that if a smoker stops consuming nicotine, his brain is left with a deficit of the chemical, which makes him feel irritable, depressed and anxious. This makes it even more likely that he\u2019ll have another cigarette to stave off withdrawal. Genetics and Addiction Addiction and genetics are closely linked. The reason some people can smoke a few cigarettes socially without becoming addicted is thought to be that some are more susceptible to addiction overall. Numerous genes are thought to increase susceptibility to addiction, and the fact that there isn\u2019t one clear-cut \u201caddiction\u201d gene makes identifying individuals who are at risk even more difficult. There are also many other factors that can lead people to addiction, so having a \u201crisk\u201d gene doesn\u2019t mean you\u2019ll become addicted and it\u2019s also possible to become addicted without having a genetic marker. Despite this, it\u2019s clear that if researchers are able to identify the underlying biological factors that could contribute to addiction, it would be possible to focus prevention efforts on those most at risk. The New Research This is where the new study comes in. Post-doctoral fellow Dan Belsky led the research, which compared the genes of heavy smokers with those of light smokers to identify specific genetic differences between the two groups. The researchers looked at the genes that\u00a0 impact the way the brain deals with nicotine, and were able to create a score for the genetic predisposition to nicotine addiction. Surprisingly, the researchers found that people rated \u201chigh risk\u201d for nicotine addiction based on their genetic make-up were not actually more likely to start smoking in the first place. The study also found that if somebody with a genetic predisposition first tried smoking as an adult, he or she was not more likely than \u201clow risk\u201d individuals to develop a nicotine addiction. This doesn\u2019t mean that the genetic risk factors are meaningless, however, because the researchers found that high-risk teens and young adults who started smoking were significantly more likely to develop an addiction. This was the main finding of the research, and additional studies will need to be conducted to determine exactly why the risk factors seem to be more important to teens and young adults. The assumption is that teens may be at additional risk because their brains are still developing, but this has yet to be confirmed. What Does it Mean? If the finding can be replicated in other research (and hopefully expanded upon), it could bring about a major change in how tobacco prevention measures are targeted. The result from the study should still serve as a wake-up call, showing the importance of focusing interventions on young smokers, rather than those who may start as adults. The implication is that these individuals are the ones who struggle the most to quit, so preventing them from getting started in the first place could drastically reduce the number of smoking-related deaths in the U.S. The similarity between the neurological mechanism for nicotine addiction and for most drug addictions could also mean that the same type of approach could work for numerous substances.