Reward Processing Behavior In Depressed Participants Relative To Healthy Volunteers: A Systematic Review And Meta-Analysis (Vol 77, Pg 1, 2020)

Key PointsQuestionAre patients with depression associated with impairment on behavioral tests of reward processing compared with healthy control individuals? FindingsIn this systematic review and meta-analysis of data from 48 case-control studies of reward-processing tasks, patients with depression showed a small to medium impairment in reward processing across all tasks. They showed medium to large impairments in reward bias, small to medium impairments in option valuation and reinforcement learning, and small (nonsignificant) impairments in reward response vigor. MeaningIn this systematic review and meta-analysis, depression is associated with behavioral reward-processing impairments, although this could vary depending on the precise subcomponent measured.ImportanceDysfunctional reward processing is a leading candidate mechanism for the development of certain depressive symptoms, such as anhedonia. However, to our knowledge, there has not yet been a systematic assessment of whether and to what extent depression is associated with impairments on behavioral reward-processing tasks. ObjectiveTo determine whether depression is associated with impairments in reward-processing behavior. Data SourcesThe MEDLINE/PubMed, Embase, and PsycInfo databases were searched for studies that investigated reward processing using performance on behavioral tasks by individuals with depression and nondepressed control groups, published between January 1, 1946, and August 16, 2019. Study SelectionStudies that contained data regarding performance by depressed and healthy control groups on reward-processing tasks were included in the systematic review and meta-analysis. Data Extraction and SynthesisSummary statistics comparing performance between depressed and healthy groups on reward-processing tasks were converted to standardized mean difference (SMD) scores, from which summary effect sizes for overall impairment in reward processing and 4 subcomponent categories were calculated. Study quality, heterogeneity, replicability-index, and publication bias were also assessed. Main Outcome and MeasuresPerformance on reward-processing tasks. ResultsThe final data set comprised 48 case-control studies (1387 healthy control individuals and 1767 individuals with major depressive disorder). The mean age was 37.85 years and 58% of the participants were women. These studies used tasks assessing option valuation (n=9), reward bias (n=6), reward response vigor (n=12), reinforcement learning (n=20), and grip force (n=1). Across all tasks, depression was associated with small to medium impairments in reward-processing behavior (SMD=0.345; 95% CI, 0.209-0.480). When examining reward-processing subcomponent categories, impairment was associated with tasks assessing option valuation (SMD=0.309; 95% CI, 0.147-0.471), reward bias (SMD=0.644; 95% CI, 0.270-1.017), and reinforcement learning (SMD=0.352; 95% CI, 0.115-0.588) but not reward response vigor (SMD=0.083; 95% CI, -0.144 to 0.309). The medication status of the major depressive disorder sample did not explain any of the variance in the overall effect size. There was significant between-study heterogeneity overall and in all subcomponent categories other than option valuation. Significant publication bias was identified overall and in the reinforcement learning category. Conclusions and RelevanceRelative to healthy control individuals, individuals with depression exhibit reward-processing impairments, particularly for tests of reward bias, option valuation, and reinforcement learning. Understanding the neural mechanisms driving these associations may assist in designing novel interventions.This systematic review and meta-analysis evaluates whether depression is associated with impairments in reward-processing behavior.