Changes in internal states across the binge-vomit cycle in bulimia nervosa.

While there is considerable evidence that bulimic behaviors serve the function of modifying internal states (e.g., satiety, mood), there is less clarity over the roles of the different behaviors across the binge-purge cycle. The present study examines the impact of bingeing and vomiting upon these internal states at different time points, and evaluates the potential reinforcement of those behaviors by the changes in internal states. Twenty-three women with diagnoses of bulimia nervosa completed a diary of all binge-vomit episodes over the course of 7 days, rating their internal states (satiety, negative mood, positive mood) at four time points during each episode. There were substantial changes across the cycle in levels of hunger, fullness, guilt/shame, anxiety/worry, and happiness/relief, but not in other states. The changes indicate that the binge-vomit cycle is maintained by the effects of both behaviors, but that the vomiting behavior evokes the strongest pattern of reinforcement. Further research is needed to determine the levels of internal states during the binge itself.