Individuals with major depression (MDD) exhibit low levels of motivation across most domains. For instance, regardless of the gains they may receive by engaging in a rewarding task, people who have symptoms of depression tend to be less likely to engage in those activities than people with no history of depression. This lack of motivation, also known as anhedonia, is a central symptom of MDD. However, it is unclear whether anhedonia is caused by an impaired ability to experience enjoyment or other factors. To further explore this dynamic, Michael T. Treadway of the Department of Psychiatry at McLean Hospital at the Harvard Medical School recently led a study evaluating motivation toward rewards in a sample of 20 adult participants with MDD and compared their responses to 15 nondepressed controls.
Treadway used the Effort Expenditure for Rewards Task (EEfRT) to determine the level of motivational effort the participants expended in order to achieve specific financial rewards. He found significant differences between the two groups of participants. Treadway said, “Individuals with current MDD were less willing to expend effort for the opportunity to earn larger monetary rewards as compared with healthy controls.” Additionally, the MDD group had more difficulty processing the reward/cost information which made the decision-making process more arduous. The lack of motivation experienced by the MDD group supports evidence that has shown motivation-targeting treatments can produce desirable results in individuals with depressive symptoms.
Another finding of the study was the blunted sensitivity of the MDD group. In particular, the participants with MDD were less stimulated by the size of the reward or their chances of winning the rewards. These motivational impairments were most pronounced in the participants with the longest course of MDD. The results of this study suggest that symptom severity and illness history directly influence the motivational behaviors of people with depression. Treadway believes that integrating reward response tasks into diagnostic criteria could help identify those at risk for developing MDD.
Treadway, M. T., Bossaller, N. A., Shelton, R. C., Zald, D. H. (2012). Effort-based decision-making in major depressive disorder: A translational model of motivational anhedonia. Journal of Abnormal Psychology. Advance online publication. doi: 10.1037/a0028813
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