Effect of Tai Chi on Young Adults with Subthreshold Depression via a Stress–Reward Complex: A Randomized Controlled Trial

Background Subthreshold depression is a highly prevalent mood disorder in young adults. Mind–body exercises, such as Tai Chi, have been adopted as interventions for clinical depressive symptoms. However, the possible effect and underlying mechanism of Tai Chi on subthreshold depression of young individuals remain unclear. This randomized controlled study aimed to evaluate the effects of Tai Chi training and tested the combined stress and reward circuitry model for subthreshold depression. Results A total of 103 participants completed this trial, with 49 in the 12-week 24-style Tai Chi group and 54 participants in control group. Our results showed significantly lower scores on depressive symptoms ( P = 0.002) and anxiety symptoms ( P = 0.009) and higher scores on quality of life ( P = 0.002) after Tai Chi training. There were significant reductions in salivary cortisol levels ( P = 0.007) and putamen gray matter volume ( P < 0.001) in the Tai Chi group. The changes in cortisol levels and putamen gray matter volume had direct (bootstrapping confidence interval [− 0.91, − 0.11]) and indirect effects (bootstrapping confidence interval [− 0.65, − 0.19]) on the changes induced by Tai Chi training on depressive symptoms, respectively. Conclusion The stress–reward complex results indicated an interaction between lowering stress levels and increasing reward circuitry activity associated with the alleviation of depressive symptoms among participants. The 12-week Tai Chi training was effective in improving the symptoms and quality of life of young adults with subthreshold depression. Trial Registration Chinese Registry of Clinical Trials (Registration Number: ChiCTR1900028289, Registered December 12, 2019).