Research Review: altered reward function in adolescent depression: what, when and how?

Abstract

Background: Conceptual models and recent evidence indicate that neural response to reward is altered in depression. Taking a developmental approach to investigating reward function in adolescent depression can elucidate the etiology, pathophysiology and course of depression, a disorder that typically begins during adolescence and has high rates of recurrence.

Methods: This conceptual review describes the what, when and how of altered reward function in adolescent depression. With the goal of generating new, testable hypotheses within a developmental affective neuroscience framework, we critically review findings and suggest future directions. Peer-reviewed empirical papers for inclusion in this critical review were obtained by searching PubMed, PsycInfo and ScienceDirect for the years 1990-2010.

Results: A pattern of low striatal response and high medial prefrontal response to reward is evident in adolescents and adults with depression. Given the salience of social stimuli for positive affect and depression, reward function might be especially disrupted in response to social rewards. Because of changes in the dopamine system and reward function with aging, altered reward function in depression might be more evident during adolescence than later in life; however, low reward function may also be a stable characteristic of people who experience depression. Mechanisms of altered reward function in depression could include disrupted balance of corticostriatal circuit function, with disruption occurring as aberrant adolescent brain development.

Conclusions: Future studies should examine responses to social rewards; employ longitudinal and prospective designs; and investigate patterns of functional connectivity in reward circuits. Understanding altered reward function in depression has potential implications for treatment development. A more rigorous approach to investigating anhedonia, threat-reward interactions and comorbid anxiety will be valuable to future progress in describing the role of reward function in the pathophysiology of depression.

Figure 1

Neural reward circuitry, with an emphasis on regions found to have altered function in depression. Adapted from Clapp et al., 2008.

Figure 2

Conceptual model of reward function across the lifespan, depicted separately for depressed and non-depressed populations. Arrows indicate timing of hypothetical depressive episodes. Between-group differences are most evident during adolescence, when levels of reward function are particularly high in the non-depressed group. At the same time, reward function in the depressed group is fairly stable across development and clinical course. Units are arbitrary.