Impairment in reward-processing subcomponent categories is associated with tasks assessing option valuation, reward bias, and reinforcement learning.
A major depressive disorder (MDD) diagnosis could foretell impairments in reward-processing.
A team, led by D. Chamith Halahakoon, MBChB, Institute of Cognitive Neuroscience, University College London, determined whether depression is linked to impairments in reward-processing behavior.
While dysfunctional reward processing is a leading candidate mechanism for the development of certain depressive symptoms, including anhedonia, there has not yet been a systematic assessment of whether and to what extent depression is associated with impairments on behavioral reward-processing tasks.
The investigators examined several databases for studies investigating reward processing using performance on behavioral tasks by individuals with depression and non-depressed control groups, published between January 1946 and August 2019.
Ultimately, they included studies that contained data regarding performance by depressed individuals on reward-processing tasks, with healthy control groups.
The investigators converted summary statistics comparing performance between depressed healthy groups on reward-processing tasks to standardized mean difference (SMD) scores. From here, the researchers calculated summary effect sizes for overall impairment in reward processing and 4 subcomponent categories.
Overall, they identified 48 case-control studies involving 1387 health control individuals and 1767 participants with major depressive disorder. The mean age of the patient population was 37.85, with 58% of the participants being women.
A total of 9 studies used tasks assessing option valuation, 6 focused on reward bias, 12 looked at reward response vigor, 20 used reinforcement learning, and 1 study focused on grip force.
Across all tasks, depression was linked to small or medium impairments in reward-processing behavior (SMD = 0.345; 95% CI, 0.209-0.480).
When examining reward-processing subcomponent categories, impairment was linked to 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).
However, impairment was not associated with reward response vigor (SMD = 0.083; 95% CI, −0.144 to 0.309).
The medication status of the MDD sample did not explain any of the variance in the overall effect size, but there was significant between-study heterogeneity overall and in all subcomponent categories other than option valuation. The investigators also found significant publication bias overall and in the reinforcement learning category.
“Relative to healthy control individuals, individuals with depression exhibit reward-processing impairments, particularly for tests of reward bias, option valuation, and reinforcement learning,” the authors wrote. “Understanding the neural mechanisms driving these associations may assist in designing novel interventions.”
Currently, depression is the leading cause of disability globally. However, the effectiveness of therapeutic agents for depression is limited and a lack of detailed understanding of the mechanisms underlying depressive symptoms, such as low mood, fatigue and anhedonia is a major challenge in the development of more effective treatment strategies.
It is also well established that depression is associated with disrupted cognitive processing, for both nonaffective and affective information, including reward processing.
The study, “Reward-Processing Behavior in Depressed Participants Relative to Healthy Volunteers,” was published online by JAMA Psychiatry.