May 16, 2011 -- Quitting smoking is never easy, but some smokers have an even harder time kicking the habit, and now new research suggests that they may derive more pleasure form nicotine.
The new study, which appears in the Proceedings of the National Academy of Sciences, may also help foster the development of more effective quitting strategies for certain smokers.
Researchers used PET scans to capture images of the number of “mu-opioid receptors” in the brains of smokers. Smokers with greater numbers of these receptors seem to derive more pleasure from nicotine, and as a result may have a harder time quitting.
“The brain’s opioid system plays a role in smoking rewards, and quitting smoking and some of the variability in our ability to quit among smokers is attributable to genetic factors,” says study researcher Caryn Lerman, PhD, director of Tobacco Use Research Center at the University of Pennsylvania in Philadelphia.
“The ability to quit smoking is influenced by a number of psychological, social, and environmental factors, but also genetic factors,” she says. “For some people, genetic variations may make it more difficult to quit than for someone else who smokes the same amount for same amount of time,” Lerman says.
The study findings are more applicable to quitting smoking than becoming addicted in the first place, she says.
New Quitting Strategies/Tools Needed
There may be a role for personalized medicine when it comes to smoking cessation, Lerman says. Personalized medicine takes the trial and error out of matching treatments by making decisions based on genetic profiles.
“Based on a person's genetic background, we can select the optimal treatment,” she says. “It is a two-pronged approach of developing new medications and being able to make the best choice for a particular person based on existing options."
Importantly, even diehard smokers should not take these findings to mean they can’t quit, she says.
“Don’t become fatalistic,” she says. “You may need particular approaches tailored to you,” she says. Going forward, “we hope to study this pathway in more detail to understand whether examining genetic background and the numbers of brain receptors can help us choose the right treatments for the right individual.”
Raymond S. Niaura, PhD, an associate director for science at the Schroeder Institute of the American Legacy Foundation, an antismoking group based in Washington, D.C., says that “there are genetic influences involved in becoming addicted to nicotine and tobacco and on how hard it is to quit smoking.”
The new findings provide “a peek into the genetic and underlying brain processes responsible for nicotine addiction,” he says.
People with this particular genetic variation may benefit from extended treatment, he says. “They may have a certain kind of sensitivity to nicotine, which could explain why they became addicted in the first place and why they may need to use nicotine replacement for a longer time than others.”
Daniel Seidman, PhD, assistant clinical professor of medical psychology and the director of Smoking Cessation Services at Columbia University Medical Center in New York City, agrees.“There are a lot of smokers and everybody gets lumped together, but there are a lot of patterns like with other types of addiction.”
This paper “points to a biological or genetic substrate which predisposes some people to have a hard time,” he says. Quitting smoking can be emotionally charged, he says. Symptoms typically include irritability, anger, and sad mood. “Some people are able to rally more and some may not bounce back as well because they have a harder time finding alternative sources of pleasure,” he says.
Agreeing with Niaura, Seidman says that some smokers seem to need nicotine replacement for longer periods of time. “When they come off nicotine patches or gum, it doesn’t feel right and it may be related to this subtype,” he says. “This is not a problem because nicotine replacement doesn’t cause cancer or go into your lungs.”