Effects of exercise on cravings and prefrontal brain responses to smoking cues in overnight abstinent and sated smokers
Monroe, Derek Christopher
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Nearly one-fifth of Americans report smoking cigarettes. Habitual cigarette smokers depend on smoking to improve affect and cope with daily emotional stressors, yet smoking is the leading cause of preventable death in the United States. Tobacco withdrawal syndrome is marked by negative affect, increased mood disturbance (e.g., fatigue, irritability, confusion, anger), and heightened sensitivity to smoking-related cues, making cessation difficult. Exercise during abstinence tempers withdrawal symptoms, and physically active smokers have higher rates of successful cessation. The mechanisms underlying the effects of exercise on withdrawal symptoms, cravings, and cue response are poorly understood, but they are plausibly related to processes in dorsolateral prefrontal cortex (DLPFC). This dissertation was designed to elucidate the relationship between mood, affective response, and DLPFC response to emotional scenes and smoking cues after exercise among smokers. The purpose of the first study was to evaluate mood, affective response, and DLPFC response to emotional scenes and smoking cues before and after smoking a cigarette and a bout of cycling exercise. The results indicate that, compared to seated rest, 20 minutes of cycling at a preferred intensity after smoking improved subjective energy, reduced anger, and suppressed DLPFC response to emotionally arousing scenes. This finding may be clinically important for individuals who desire to quit and might use exercise as a way to manage mood and emotional responsiveness. The purpose of the second study was to evaluate the effect of vigorous exercise on mood, cravings, and DLPFC response to affective scenes and smoking cues, and their relationships, after overnight abstinence. Results from the second study indicate that cravings, DLPFC sensitivity to unpleasant scenes, and total mood disturbance were increased by overnight abstinence, and 20 minutes of vigorous intensity cycling, increased subjective energy and attenuated cravings. In addition, 70% of the reduction in desire for a cigarette was explained by increased feelings of energy, and 30% of the reduction in desire for a cigarette was explained by right DLPFC response to smoking cues. The findings of this dissertation are consistent with evidence that a single bout of exercise reduces cravings in smokers. The results extend previous findings by demonstrating that mood disturbance and cravings are closely related during short-term smoking withdrawal and that increased energy and cue-induced avoidance motivations in the DLPFC contribute to reduced cravings after exercise. Furthermore, exercise after a single cigarette protects against mood disturbance and sensitivity to emotional elicitors that plausibly contribute to continued smoking behavior.