Examining effects of effort and reward magnitude on effort-cost decision-making in people with major depressive disorder.

Motivational impairment is a primary feature of major depressive disorder (MDD); yet the cognitive mechanisms underlying this deficit remain unclear. Effort-cost decision making is a popular framework for understanding motivation in MDD. This study examined the relative contributions of reward and effort to decision-making in an effort-cost decision-making (ECDM) task. A combined sample (remitted and current) of medicated and nonmedicated individuals with MDD (N = 32) and healthy controls (HC, N = 30) completed the Apple Gathering Task. In this task, reward and effort magnitudes are parametrically manipulated to independently estimate effects of effort and reward on choice. Choice data were analyzed by using conventional analyses, as well as computational models of behavior. Compared with HC, individuals with MDD were less willing to accept offers characterized by low reward and high effort amounts. Computational analyses using hierarchical drift diffusion modeling mirrored these findings, suggesting that evidence accumulation in MDD compared with HC was 1) faster when rejecting high effort options, and 2) faster when accepting high reward options. Additionally, higher fatigue and presence of a current depressive episode was associated with reduced ECDM in those with MDD, for low reward and high effort offers. Our results highlight influences of both reward and effort on reduced ECDM in MDD. Furthermore, our results point to critical symptom (fatigue) and state-based associations (current vs. remitted status).