Brain imaging reveals changes when smokers focus on long-term consequences of their tobacco use.
Addiction makes it difficult for people to look beyond immediate gratification to the longer term consequences of their actions. Accordingly, patients in drug abuse treatment are often coached to make and rehearse mental associations between situations that trigger drug cravings and the problems that are likely to ensue from succumbing to them. The cognitive behavioral programs that incorporate this strategy generally are effective, but researchers have shed little light on the neurological basis for their efficacy—until now.
In a study led by Dr. Kevin N. Ochsner of the Social Cognitive Neuroscience Laboratory at Columbia University, smokers reported milder cigarette cravings when they thought about smoking’s harmful effects while viewing smoking cues than when they focused on its pleasures. Brain imaging correlated the reductions in craving with altered activity levels in regions associated with emotional regulation and reward.
Mental Adjustment Alters Brain Activity
Dr. Ochsner and colleagues recruited smokers as study subjects because smoking accounts for more illness and death than any other addiction. To gain insight on the smokers’ ability to regulate cravings in general, the team also investigated their responses to cues for high-fat food.
The participants were 21 men and women who had smoked for 10 years, on average, and were not trying to quit. In preparation for the study, the participants practiced turning their thoughts to rewarding effects of cigarettes or high-fat food consumption when given the instruction “NOW” and to negative effects when given the instruction “LATER.” In the study itself, the researchers gave each participant 100 such instructions, in random order, each followed by a 6-second exposure to a screen image of either cigarettes or food. Then, after a 3-second delay with the screen blank, the participant reported how much he or she desired to smoke or eat, on a scale of 1 (not at all) to 5 (very much).
The power of thinking about negative effects proved to be considerable. The participants reported 34 percent less intense urges to smoke and 30 percent less intense food cravings after the LATER instruction compared with the NOW instruction.
Brain scans taken during the experiment showed how concentrating on long-term negative consequences alters brain activity to reduce craving. Functional magnetic resonance imaging (fMRI) of the participants’ whole brain revealed increased activity levels in areas—the dorsomedial, dorsolateral, and ventrolateral regions of the prefrontal cortex (PFC)—that support cognitive control functions, such as focusing, shifting attention, and controlling emotions. Activity decreased in regions that previous studies have linked with craving; these areas include the ventral striatum and ventral tegmental area, which are parts of the reward circuit; the amygdala; and the subgenual cingulate. Individual participants who reported larger reductions in craving exhibited these changes to a more marked degree. A specialized mediation analysis of the images found that the increase in PFC activity drove the decrease in ventral striatum activity, which, in turn, fully accounted for the reduction in craving.
“These results show that a craving-control technique from behavioral treatment influences a particular brain circuit, just as medications affect other pathways,” says Dr. Steven Grant of NIDA’s Division of Clinical Neuroscience and Behavioral Research.
The researchers noted that the study participants reduced their smoking and food cravings to the same extent, even though smoking cravings were initially more intense. This finding suggests that calling undesirable consequences to mind has potential to help people overcome a variety of unhealthy urges.
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This is a two-part illustration. On the left is a bar graph showing how study participants rated their craving level on a scale of 1 (low) to 5 (high), represented on the Y axis. The first bar shows that when participants focused on the immediate rewards of smoking, they reported an average of about 4.2. When participants thought of the long-term negative consequences of smoking, they reported an average craving of only about 2.8. On the right side of the illustration, one a brain scan shows the dorsolateral prefrontal cortex in blue and is labeled: Increased Dorsolateral Prefrontal Cortex Activity. An arrow points from that image to one the shows the brain
“Cognitive reappraisal—mentally changing the meaning of an event or object to lessen its emotional impact and therefore alter the behaviors it triggers—is a strategy that helps a variety of problems,” says Dr. Ochsner. Cognitive-behavioral therapists train patients to use this approach, among others, to cope with negative emotions, stress, and substance cravings. Dr. Ochsner says, “People may not realize that they can control cravings or emotions using cognitive strategies—for example, thinking of negative consequences and distracting and distancing oneself—but patients can learn these techniques and then must continue to apply them over time.”
Dr. Ochsner says there is broad scientific interest in the neurobiological mechanisms underlying cognitive control over thoughts and emotions that promote unhealthy behaviors. Such studies generally find that although there is some overlap in the regions of the PFC engaged when people exert cognitive control, different areas seem to support different strategies for the regulation of emotional responses.
“The mediation analysis that Dr. Ochsner and colleagues conducted is unique among imaging studies and is a particular strength of this research,” says Dr. Grant. “Because the researchers examined the interaction of brain regions, the results provide a perspective on the neural circuits involved in cognitive control of craving.”
Dr. Grant suggests two important next steps in this area of research: identifying why some people have more problems than others in controlling the desire for cigarettes and determining whether brain activity predicts the ability to quit smoking.
Kober, H., et al. Prefrontal-striatal pathway underlies cognitive regulation of craving. Proceedings of the National Academy of Sciences 107(33):14811–14816, 2010. Full Text (PDF,369KB)
Kober, H., et al. Regulation of craving by cognitive strategies in cigarette smokers. Drug and Alcohol Dependence 106(1):52–55, 2010. Full Text