The Optimal Exercise Modality and Dose for Cortisol Reduction in Psychological Distress: A Systematic Review and...

Objectives: Psychological distress has been linked to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and altered cortisol secretion. Exercise is increasingly recognized as a non-pharmacologic strategy for stress regulation. This systematic review and network meta-analysis assessed the relative efficacy of different exercise modalities and the optimal dose in modulating cortisol levels in adults with psychological distress. Methods: We systematically searched five databases up to 30 June 2025 for relevant randomized controlled trials. Two reviewers independently conducted study selection, data extraction, and risk-of-bias assessments. Pairwise meta-analyses and a frequentist network meta-analysis were performed with random-effects models. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated. Dose-response relationships were examined, and the certainty of evidence was evaluated using the GRADE framework. Results: Forty-four studies were included. Overall, exercise was associated with moderate cortisol reductions. Yoga demonstrated the greatest effect (SMD = -0.59; 95% CI = -0.90 to -0.28; SUCRA = 93%), followed by qigong and multicomponent exercise. High-intensity interval training tended to increase cortisol levels, although not significantly. The dose-response analysis revealed an inverted U-shaped relationship, characterized by an optimal response at approximately 530 MET-min/week, and longer intervention duration predicted greater reductions. The certainty of evidence ranged from very low to high, with yoga-control comparisons supported by the strongest evidence. Conclusions: Exercise, particularly mind-body practices such as yoga and qigong, can reduce cortisol levels in individuals with psychological distress. The dose-response relationship exhibited a non-linear pattern, with optimal efficacy observed at approximately 530 MET-min/week. Nevertheless, further high-quality trials are required to confirm the optimal modality and dose.