The reward system in late-life depression : reactions to reward and punishment : a cross-sectional case-control study

Abstract

Dysfunction in reward-related areas, such as the mesocorticolimbic DA system in depressed patients was observed across studies. A limited number of studies were conducted on the reward system dysfunction in Late-Life Depression(LLD). However, the reward system is closely related to the underlying cause of LLD, including aging, cerebrovascular diseases, and White matter hyperintensity(WMH). So LLD patients may also suffer from reward system dysfunction. Reward system dysfunction is important not only does it is closely related to the causes of LLD, but also because it predicts poor treatment outcomes. To compare the reward system function in LLD patients with psychiatrically healthy control, standardized computer tests, namely probabilistic reward task(PRT) and door opening task were carried out in this study. Furthermore, cognitive functions and anhedonia were also measured by clinical assessments to study their relationship with the reward system. 53 LLD patients and 54 psychiatrically healthy control were recruited for this study. Standardized computer tests including PRT and Door Opening task was applied. PRT measures the sensitivity to reward and reward learning, while the Door Opening Task measures Reward Responsiveness, sensitivity to reward, and sensitivity to punishment. The task performance of the LLD group and the control group was compared. Clinical assessments that measure cognitive function and anhedonia were also carried out. Linear Regression analyses were applied to the result of the clinical assessments and the computer test performances. First, no significant difference was found in reward task performances between the patient and the control group. Second, the Snaith-Hamilton pleasure scale (SHAPS) and Apathy Evaluation Scale, Clinician Version(ASEC) score is not correlated with the PRT result, but the AES-C score is positively correlated to the lose latency in the door opening task. Lastly, there are correlations between the reward test scores and some domains of cognitive function. There is no significant difference between the LLD and the control group in both reward tasks, which is probably explained by the severity of depressive symptoms, particularly the anhedonia level. In addition, Cognitive function is suggested to be correlated with the reward system function in LLD. Further studies are necessary to clarify the relationship between cognition and the reward system so intervention can be carried out to treat LLD more efficiently, further studies on anhedonia and the reward system is also needed as the SHAPS scores are low in the patient group