Neurobiological Reward-Related Abnormalities Across Mood Disorders

This chapter provides a critical review of recent behavioral and neuroimaging evidence of reward processing abnormalities in mood disorders. The primary focus is on the neural mechanisms underlying disruption in approach motivation, reward learning, and reward-based decision-making in major depression and bipolar disorder. Efforts focused on understanding how reward-related impairments contribute to psychiatric symptomatology have grown substantially in recent years. This has been driven by significant advances in the understanding of the neurobiology of reward processing and a growing recognition that disturbances in motivation and hedonic capacity are poorly targeted by current pharmacological and psychotherapeutic interventions. As a result, numerous studies have sought to test the presence of reward circuit dysfunction in psychiatric disorders that are marked by anhedonia, amotivation, mania, and impulsivity. Moreover, as the field has increasingly eschewed categorical diagnostic boundaries in favor of symptom dimensions, there has been a parallel rise in studies seeking to identify transdiagnostic neural markers of reward processing dysfunction that may transcend disorders. The thesis of this chapter is twofold: First, evidence indicates that specific subcomponents of reward processing map onto partially distinct neurobiological pathways. Second, specific subcomponents of reward processing, including reward learning and effort-based decision-making, are impaired across different mood disorder diagnoses and may point to dimensions in symptom presentation that possess more reliable behavioral and neural correlates. The potential for these findings to inform the development of prevention and treatment strategies is discussed.