Neurobiological and Psychological Maintenance Mechanisms Associated With Anticipatory Reward in Bulimia Nervosa

Bulimia nervosa (BN), an eating disorder characterized by recurrent bulimic episodes of binge eating and often persists in spite of treatment, likely indicating ineffectively targeted maintenance mechanisms. Treatment outcome data suggest that < 30-45% of adults who receive treatment for BN exhibit prolonged remission. Further, BN is often characterized by a worsening course in which symptom severity increases with duration of illness. Intervention advances require identification of both the mechanisms that underlie reward derived from bulimic behavior and the mechanisms that maintain these behaviors over time. Current treatments for BN focus on immediate antecedents and consequences of bulimic behavior, despite the possibility that the reward derived from these behaviors may occur well before this point during the anticipation of binge eating and purging. A majority (>75%) of individuals with BN report "planning" some or most of their bulimic episodes. Thus, determining the role of reward anticipation in BN will facilitate the application of novel interventions that more precisely target these neglected mechanisms. Further, research indicates that reward mechanisms become increasingly focused on anticipation in later phases of reward learning. Therefore, it is important to determine how reward anticipation processes contribute to the maintenance of bulimic behaviors and interact with illness duration to facilitate BN chronicity. The purpose of this investigation is to identify the potentially crucial role of anticipatory reward mechanisms maintaining bulimic behavior (i.e., binge eating and purging) in bulimia nervosa (BN). The research will investigate neural and psychological anticipatory processes in BN, both in the scanner and the natural environment.

Inclusion criteria

Bulimia nervosa (BN) and healthy control (HC) groups:

• Right-handed
• Ability to read and speak in English

BN group only:

• Eating Disorder Examination (EDE) diagnosis of BN (i.e., at least one objective bulimic episode and one self-induced vomiting episode per week for at three months) with binge episodes always accompanied by self-induced vomiting
• Stable dose for at least 6 weeks of any recent changes in medication impacting mood, appetite, or weight

HC group only:

• No binge eating or purging episodes for the past three months on the EDE
• No current or past history of an eating disorder as diagnosed by Structured Clinical Interview for DSM-5 Disorders

Exclusion criteria

• History of gastric bypass surgery
• Medical condition acutely affecting eating behavior and/or weight (i.e., pregnancy, lactation, thyroid disease)
• Current medical or psychiatric instability (i.e., hospitalization required in the past three months)
• Lifetime history of psychosis or bipolar disorder
• History of neurological disorder or injury (i.e., stoke, head injury with >10 minutes loss of consciousness)
• Current substance use disorder
• BMI less than 19 kg/m^2
• Acute suicidality requiring hospitalization
• fMRI exclusions as specifiedd by the Center for Magnetic Resonance Research
• Food allergy that cannot be accommodated through substitutions to the laboratory test snack