Nicotine is so addictive, according to Dr. J. Lee Westmaas, the scientific director for behavioral research at the American Cancer Society, because of how it affects the brain. "[Nictone] impacts levels of serotonin and dopamine in the brain, which are neurotransmitters involved in feelings of pleasure, appetite, sleep, and other important functions," Westmaas said. "Consuming nicotine causes a release of dopamine, which is central to invoking the reward pathways of the brain." According to Westmaas, there are many reasons why it can be challenging for some people to quit smoking. For example, if a person has smoked for a long time, they are likely more dependent on nicotine. As a result, they may experience more intense withdrawal symptoms, resulting in smoking again to relieve those symptoms. Also, a person's social or physical environment could affect whether they are able to quit. But despite smoking being a hard habit to break for so many, for others, it's as simple as quitting cold turkey. And a group of researchers believes much of this has to do with genetics. Victoria Risner was the primary researcher on a study conducted by psychologists at Emory University and published by Nicotine & Tobacco Research that examined the genetic risk of nicotine dependence. Risner, currently a medical student at the University of North Carolina at Chapel Hill, analyzed a collection of data for months; the data contained information about people with various traits, genes and disorders that lead to other addictions. Next, Risner and her fellow researchers looked for matching variants in genetic data from a national representative sample of Americans diagnosed with nicotine dependence. At the end of the study, the results showed how different traits and disorders raised or lowered the risk of nicotine dependence. "A couple of our phenotypes (a phenotype is the set of observable characteristics or traits of an organism) were substance use-related," Risner explained. "We include alcohol use disorder, but we also included some phenotypes that are not related to substance use, like neuroticism, which is a personality trait often associated with anxiety disorders, depression, as well as schizophrenia." "And the reason we used these traits is that there's been previous research that has indicated that those phenotypes have a genetic underpinning and are correlated with nicotine dependence. Because of this, you can assume via that relationship, that there are shared genetic variants that can contribute to both diseases," Risner said. The study concluded that those with a higher risk of diseases and conditions like schizophrenia, depression, self-reported risk-taking, and even high body mass index were all indicators of a higher risk for nicotine dependence. "Obviously, there are going to be some environmental effects for somebody's risk for developing nicotine dependence," Risner said. "For example, you have to initiate using some nicotine product. Still, there are a lot of genetic underpinnings on who actually goes on to develop an addiction, and I think that's really important for destigmatizing addiction in general. Especially with nicotine dependence," Risner said. Risner and her fellow researchers hope their study helps boost the understanding of nicotine dependence and that other researchers build off their model. They also dream of the day when clinicians can provide a genetic test to assess a person's risk for nicotine dependence.