The impact of stress on delay discounting in bulimia nervosa or alcohol use disorder – a functional magnetic resonance imaging study

Background:Stress could induce neurobiological changes in patients with bulimia nervosa (BN) and alcohol use disorder (AUD) that increase delay discounting (DD), making the short-term benefits of coping through eating or drinking outweigh long-term negative consequences. Therefore, this study explores differences in DD between patients (BN or AUD) and healthy controls (HC), the impact of stress on food and alcohol DD, and the associated changes in brain activity.Methods:A total of 102 female participants (AUD: 27, BN: 25, HC: 50; age range: 18-38 years) underwent repeated fMRI scanning while performing three DD tasks (DDT). Initially, all participants performed a monetary DDT. Then, participants performed a food or alcohol DDT before and after stress induction with the Montreal Imaging Stress Task (MIST). Specifically, patients with BN completed a food DDT,patients with AUD completed an alcohol DDT and HC were randomly allocated to either DDT.Results:No differences were found in the DD of money, food or alcohol between patients and controls before stress. However, stress increased the DD of alcohol in patients with AUD, but not in HC. Stress also increased the DD of food in HC, but not in patients with BN. Furthermore, stress caused patients with AUD to display a lower activity of the right supplementary motor area while discounting alcohol. Stress also caused HC to display a lower activity of the middle/super frontalcortex and a higher activity of the motor cortex while discounting food, but caused patients with BN to display a higher activity of the occipital cortex.Conclusion:The results suggest that stress induces neurobiological changes in patients with AUD which cause them to prefer more immediately available alcohol. However, the results observed in patients with BN suggest a more complex relation between stress and food.