Effects of high‐intensity interval training on depressive and anxiety symptoms in healthy individuals: A systematic review and meta‐analysis of randomized clinical trials

Although evidence regarding the effects of high-intensity interval training (HIIT) on mental health has increased in recent years, there is still no consensus regarding the effects of HIIT on the symptoms of depression and anxiety in a healthy population. Therefore, this systematic review aimed to investigate the effects of HIIT on depressive and/or anxiety symptoms in healthy individuals. The following four databases were searched: PubMed, Scopus, Embase, and PsycINFO. Only randomized clinical trials (RCTs) were included. We performed a random-effects meta-analysis based on standardized mean difference (SMD). The risk of bias was assessed using the RoB 2.0 tool, and the certainty of the evidence was evaluated based on recommendations GRADE. Eight RCTs evaluating 471 participants (81% female) were considered eligible for inclusion. The results of the meta-analysis showed that HIIT-based interventions had no significant effect on reducing anxiety (SMD = -0.17; 95% CI: -0.53, 0.19; p = 0.27) and depressive symptoms (SMD = -0.38; 95% CI: -1.06, 0.30; p = 0.17) compared with the passive control group. In conclusion, HIIT does not improve symptoms of depression and anxiety in healthy individuals. This finding is based on evidence of very low certainty. Therefore, the evidence is still not consistent enough to support HIIT as a viable strategy to reduce both outcomes because of the limited number of included studies and the overall quality of evidence.