An Integrated Sleep and Reward Processing Model of Major Depressive Disorder

Major depressive disorder with comorbid sleep disturbance has been associated with negative outcomes, including lower rates of treatment response and a greater likelihood of depressive relapse compared to those without sleep disturbance. However, little, if any, research has been conducted to understand why such negative treatment outcomes occur when sleep disturbance is present. In this conceptual review, we argue that the relationship of sleep disturbance and negative treatment outcomes may be mediated by alterations in neural reward processing in individuals with blunted trait-level reward responsivity. We first briefly characterize sleep disturbance in depression, discuss the nature of reward processing impairments in depression, and summarize the sleep/reward relationship in healthy human subjects. We then introduce a novel Integrated Sleep and Reward model of the course and maintenance of major depressive disorder and present preliminary evidence of sleep and reward interaction in unipolar depression. Finally, we discuss limitations of the model and offer testable hypotheses and directions for future research.