Brain Scans Reveal Cause of Smokers' Cravings
Within the mind of every smoker trying to quit rages a battle between the higher-order functions of the brain wanting to break the habit and the lower-order functions screaming for another cigarette, say researchers at Duke University Medical Center. More often than not, that cigarette gets lit.
Brain scans of smokers studied by the researchers revealed three specific regions deep within the brain that appear to control dependence on nicotine and craving for cigarettes. These regions play important roles in some of the key motivations for smoking: to calm down when stressed, to achieve pleasure and to help concentration.
"If you can't calm down, can't derive pleasure and can't control yourself or concentrate, then it will be extremely difficult for you to break the habit," said lead study investigator Jed E. Rose, Ph.D., director of the Duke Center for Nicotine and Smoking Cessation Research. "These brain regions may explain why most people try to quit several times before they are successful."
Understanding how the brain responds to cigarette cravings can help doctors change nicotine cessation treatments to address all three of these components of withdrawal, Rose said. Drugs or therapies that target these regions may help smokers stave off the cravings that often spoil their attempts to quit.
The team's findings are now online in the journal Neuropsychopharmacology. The research was funded by Phillip Morris USA.
Approximately one in five Americans smokes. Even though 70 percent of smokers report that they would like to quit, only 5 percent do so successfully.
In this study, the researchers manipulated the levels of nicotine dependence and cigarette craving among 15 smokers and then scanned their brains using positron emission tomography, or PET scans, to see which areas of the brain were most active.
Three specific regions of the brain demonstrated changes in activity when the smokers craved cigarettes versus when they did not.
One region that lights up, called the thalamus, is considered to be the key relay point for sensory information flowing into the brain. Some of the symptoms of withdrawal among people trying to quit stem from the inability to focus thoughts and the feeling of being overwhelmed, and could thus be explained by changes in this region, according to the researchers. The researchers found that changes in this region were most dramatic among those who said they smoked to calm down when under stress.
Another region that lights up is a part of the pleasure system of the brain. Changes in this region, called the striatum, were most notable in people who smoked to satisfy craving and for pleasurable relaxation, the researchers said.
A third region that lights up, called the anterior cingulate cortex, is vital to cognitive functions such as conflict, self regulation, decision making and emotion. People whose brain scans showed the most differences in this region also reported that they smoked to manage their weight.
"This knowledge gives us new clues about brain mechanisms underlying addiction to cigarettes and could allow us design better methods to help smokers quit," Rose said.
Rose and his colleagues are now planning to perform brain scans on smokers undergoing nicotine replacement therapy, such as the nicotine patch, to determine how these treatments affect the same regions of the brain.