Optimal exercise modality and dose to improve depressive symptoms in adults with major depressive disorder: A systematic review and Bayesian model-based network meta-analysis of RCTs.

Depression is a growing public health concern, and exercise is an adjunctive treatment modality to improve depression, but the optimal form of exercise and the optimal dose are still unclear. This systematic review examined the efficacy of four major types of exercise (aerobic, resistance, mixed, and mind-body) on depression, as well as the dose-response relationship between total and specific exercise and depressive symptoms. We included randomized controlled trials that included participants aged 18 years or older with a diagnosis of major depressive disorder or a depressive symptom score above a threshold as determined by a validated screening measure, implemented one or more exercise therapy groups, and assessed depressive symptoms at baseline and follow-up. Forty-six studies (3164 patients) were included in the meta-analysis. Aerobic (standardised mean difference (SMD) = -0.93; 95% CI: -1.25 to -0.62) and mind-body exercise (SMD) = -0.81; 95% CI: -1.19 to -0.42) improved depressive symptoms better compared to controls, followed by mixed (SMD = -0.77; 95% CI: -1.20 to -0.34) and resistance exercise (SMD = -0.76; 95% CI: -1.24 to -0.28). This dose-response meta-analysis showed a U-shaped curve between exercise dose and depressive symptoms. The minimum effective dose was estimated to be 320 metabolic equivalent (METs) -min per week and the optimal response was 860 METs-min per week. These findings lead us to advocate that clinicians carefully select the appropriate dose of exercise based on the patient's individual characteristics and needs, in conjunction with psychological care interventions.