Neural Responsiveness To Reward And Cognitive Control Following An Eight-week Aerobic Exercise Trial For Depression

Abstract

Major Depressive Disorder (MDD) is a common affective disorder that affects nearly 20% of adults and is a leading cause of global disability and disease. Despite demonstrated efficacy of aerobic exercise for depression, there is a poor understanding of clinical and neurobiological mechanisms. Two candidate mechanisms of depression that may be modifiable through aerobic exercise are reward processing and cognitive control deficits. PURPOSE: The primary aim was to examine the effects of an 8-week aerobic exercise (AE) program on event-related potential (ERP) indices of reward processing (RewP) and cognitive control (ERN), and symptoms of depression among individuals with MDD. Secondary aims were to determine whether changes in reward (RewP) or cognitive control (ERN) were related to changes in depressive symptoms and whether baseline RewP or ERN could predict the likelihood of an antidepressant response. METHODS: Individuals with MDD (N = 51; 75% female) were stratified by depressive symptoms and randomized to either moderate-intensity AE (n = 26) or light-intensity stretching (n = 25) that was completed 3 times per week for 45 min. Depressive symptoms, aerobic fitness, and ERPs were assessed pre and post intervention. RESULTS: Compared to stretching, the AE condition resulted in pre-to-post reductions in depressive symptoms (p < .01; η2p = 0.17), while both conditions experienced pre-to-post increases in aerobic fitness (p < .01, η2p = 0.14). Although no mean-level treatment changes in RewP or ERN were observed, there was a relationship between pre-to-post change in ERN and change in depressive symptoms (r = -0.41, p < .01), indicating a decrease in ERN was related to larger pre-to-post reductions in depressive symptoms. At baseline, a larger ERN was predictive of greater pre-to-post change in depressive symptoms, (p < .05, OR = 1.27), while there was a trend for baseline RewP as a predictor of treatment response (p = .07, OR = 1.24). CONCLUSION: These findings provide support for the antidepressant effects of AE and highlight ERN as a potential neurobiological marker that predicts and tracks the antidepressant response. Future research incorporating predictors of response and examining neurobiological mechanisms may help advance understanding of the effects of exercise as a treatment for depression.