Exercise reduces depression and inflammation but intensity matters

Background: Exercise may help to mitigate symptoms of depression by reducing inflammation; however, little is known about the influence of exercise intensity on depressed mood. Methods: In the present study, sixty-one university students were assigned to six weeks of high-intensity interval training (HIT), moderate continuous training (MCT), or no exercise (CON) during their academic term. We measured changes in depression, anxiety and perceived stress along with pro-inflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), interleukin-1 beta (IL-1 beta), and C-reactive protein (CRP). Results: Depression increased for CON, demonstrating how quickly mental health can decline for students during their academic term. In contrast, MCT decreased depression and pro-inflammatory cytokine TNF-alpha levels. Although HIT decreased depressive symptoms, it also increased perceived stress, TNF-alpha and IL-6 relative to MCT. This may be due to the higher level of physical stress evoked by the more strenuous exercise protocol. Conclusions: Taken together, the results suggest that moderate-intensity exercise may be an optimal intensity of exercise for the promotion of mental health by decreasing TNF-alpha. This is critical for informing the use of exercise as medicine for mental health.