A Comparison of Bulimia Nervosa and Its OSFED Variant on Trait and Behavioural Indicators of Reward Constructs.

INTRODUCTION: Although individuals with bulimia nervosa (BN) demonstrate elevated reward sensitivity and reward valuation-effort (RV-e) compared to controls, whether BN differs from its other specified feeding or eating disorder variant (OSFED-BN), remains unclear. Further, whether differences best reflect categorical distinctions or correlations with symptom severity is unknown. This study examined whether trait and behavioural reward indicators differentiate BN, OSFED-BN, and controls, predict diagnostic status, and correlate with bulimic symptom severity. METHODS: Participants were 349 women (153 BN, 118 OSFED-BN, 78 controls). Group comparisons, multinomial logistic regression, and correlational analyses were conducted on the Sensitivity to Punishment/Sensitivity to Reward-Reward subscale (SPSRQ-Reward), Behavioural Activation System-Drive (BAS-Drive) scale, and progressive ratio tasks assessing RV-e for food and game rewards. RESULTS: BN and OSFED-BN demonstrated higher SPSRQ-Reward scores than controls but did not differ from each other. OSFED-BN, but not BN, showed higher food and game RV-e compared to controls. SPSRQ-Reward predicted higher odds of BN or OSFED-BN versus controls, whereas BAS-Drive predicted lower odds. SPSRQ-Reward was positively associated with bulimic symptom frequencies. Food RV-e was inversely associated with purging frequency. DISCUSSION: Findings supported the role of reward-related processes in contributing to both dimensional and categorical differences between BN, OSFED-BN, and controls.