Untenable Dynamics of Reward Sensitivity in Adolescents with Major Depressive Disorder

Objectives Anhedonia has been recognized as one of the core symptoms of major depressive disorder (MDD), which is associated with blunted reward sensitivity. Nonetheless, the psychopathological and computational mechanism underlying anhedonia in young patients with MDD remains uncertain. In this study, we investigated reward sensitivity in adolescents and young adults with MDD by leveraging computational modelling. Methods A total of seventy MDD patients and fifty-four age- and sex-matched healthy controls (HC) participated in a probabilistic reward task (PRT) to assess individuals' general behavioral inclination towards more frequently reinforced stimuli (i.e., “reward bias”). We adopted Bayesian hierarchical drift diffusion modelling (HDDM) to determine changes in reward sensitivity and computational process during the stage of decision-making. Results During the latter phase of the task, young patients with MDD displayed a lower level of reward bias compared to the HC group. Noteworthily, depressed adolescents exhibited a lower reward bias, while no significant between-group differences were observed in young adulthood. The HDDM analysis additionally revealed a decrease in drift rate and an increase in decision threshold among depressed adolescents, correlating with higher levels of depression and reduced hedonic capacity. Conclusions Our results implied that deficient reward sensitivity and slower evidence accumulation in reward learning could serve as potential indicators of anhedonia in adolescent patients with MDD, thereby offering insights into the developmental psychopathology of depression.