A Pilot Study of the Effects of Lisdexamfetamine Dimesylate (Vyvanse) Treatment on Reinforcement Learning in Adults With Bulimia Nervosa

Abstract

Although bulimia nervosa (BN) is thought to be associated with impairments in reward-related decision making, little is known about the decisional processes that contribute to BN behaviour. Twenty-three participants with moderate-extreme BN were administered a two-step reinforcement learning task to assess their relative degree of decisional exploration/exploitation, goal directed versus habitual control, and learning rate before and after treatment with lisdexamfetamine dimesylate (LDX). BN symptom changes were also monitored. Paired permutation tests show a statistically significant decrease in objective binge episodes (MT3-MT1= -35.11, p < 0.001) and compensatory behaviours (MT3-MT1= -38.85, p< 0.001) at maintenance drug dosage compared to baseline. However, reward learning, as far as it is assessed by the task did not seem to contribute to the effect of LDX on BN behaviour. It is hoped that these findings will contribute to an improved understanding of the computational nature of decision making among individuals with BN.