The Efficacy of Ashwagandha (Withania somnifera) for Reducing Stress and Anxiety: A Systematic Review and Meta-Analysis

Abstract

Introduction: Ashwagandha is an adaptogenic herb used in Ayurvedic medicine to manage stress. Its clinical efficacy, however, requires systematic evaluation. This review aims to synthesize the evidence from randomized controlled trials (RCTs) on the effectiveness of Ashwagandha in reducing perceived stress and anxiety in adults.

Methods: A comprehensive search of MEDLINE, PsycINFO, and AMED was conducted for all relevant literature published up to December 2019. We included placebo-controlled RCTs that assessed stress or anxiety using validated psychometric scales. Data were pooled using a random-effects model to determine the overall effect size.

Results: Eight RCTs involving 563 participants were included. The meta-analysis showed that Ashwagandha supplementation resulted in a significantly greater reduction in scores on anxiety and stress scales compared to placebo (Standardized Mean Difference [SMD] = -0.65, 95% CI: -0.88 to -0.42, p < 0.001). Additionally, several studies reported a significant reduction in serum cortisol levels in the Ashwagandha group.

Discussion: The findings suggest that Ashwagandha is an effective and safe intervention for reducing stress and anxiety. The mechanism may be related to its modulatory effect on the hypothalamic-pituitary-adrenal (HPA) axis. Limitations include small sample sizes and variability in extract standardization across studies.

Conclusion: Evidence from studies conducted before 2020 supports the use of Ashwagandha for improving an individual's resistance towards stress and anxiety. Further large-scale trials are needed to confirm these findings.