Craving and the ability to regulate it are increasingly recognized for having key roles in the maintenance of addictions (including nicotine dependence), and in the prevention of relapse. To investigate these important processes, we developed the Regulation of Craving (ROC) task1-5. In this task, nicotine-dependent smokers are exposed to smoking-related stimuli. In the craving condition, they are instructed to think of the pleasant feelings associated with smoking, which results in cigarette craving. Then, in the regulation condition, they are instructed to use a cognitive strategy to regulate their craving for cigarettes (e.g., `think of the negative consequences associated with smoking')1. We used the ROC task and functional magnetic resonance imaging (fMRI) to demonstrate that self-reported craving is significantly reduced during the regulation condition, and that this depends on recruitment of regions in prefrontal cortex associated with cognitive control, such as dorsolateral prefrontal cortex2, 6. We have also shown that recruitment of these brain regions, in turn, modulates activity in subcortical regions that underlie craving, such as the ventral striatum2, 3, 7. Stress is another key factor contributing to drug use in general and smoking in particular8. A leading hypothesis is that stress contributes to smoking and relapse by potentiating craving and neural activity in brain regions associated with craving (including ventral striatum)9-11. However, recent research suggests that stress can also impair prefrontal function12. Thus, it is possible that stress may lead to drug use via two distinct routes: by (1) potentiating craving and neural activity in craving-related regions (as shown with other addictions), and also by (2) compromising the regulation of craving via decrements to prefrontal function. To test our novel model and evaluate these alternative hypotheses, we will administer the ROC task to 84 nicotine-dependent smokers and 84 matched healthy controls in a 90-minute fMRI session. We will use threat of electric shock, which is known to induce acute stress, on half the trials. We will compare (a) self-report and (b) neural activity between craving and regulation conditions, in a 2x2x2 design: 2 ROC conditions (Craving vs. Regulation) x 2 Stress conditions (Threat of Shock vs. Safe from Shock) x 2 Stimuli (Cigarettes vs. Appetitive Food control). Exponential inter-trial intervals will ensure proper separation of neural events13, 14. To increase clinical impact we will assess the contribution of each effect (Stress on Craving vs. Regulation) to smoking severity. Finally, we will explore gender and individual differences in stress, craving, and the regulation of craving, as they may moderate effects of stress, with implications for smoking cessation. This project promises to advance our neurobiological understanding of stress, craving, and the regulation of craving, as well as their interaction and contribution to smoking. In turn, this would provide both a new theoretical framework to understand extant data on stress and substance use, and also adapt current treatments to specifically address the effects of stress on craving and its regulation.
Stress, craving, and self-regulation are three key factors in drug use in general, and cigarette smoking in particular, however, how these factors interact to increase smoking is not well understood. The proposed project will be the first to evaluate the effects of acute stress on both (1) self-report and (2) neural activity during cigarette craving as well as the regulation of craving. This promises to increase our understanding of nicotine dependence and to help us develop better therapies for this and other substance use disorders.
