The effect of Withania somnifera (Ashwagandha) on mental health symptoms in individuals with mental disorders: systematic review and meta-analysis

Background Withania somnifera (WS) is considered an adaptogen agent with reported antistress, cognition facilitating and anti-inflammatory properties, which may be beneficial in the treatment of mental disorders. Aims This systematic review investigated the efficacy and tolerability of Withania somnifera for mental health symptoms in individuals with mental disorders. Method The protocol of this review was registered with PROSPERO (CRD42023467959). PubMed, Scopus, PsycINFO, CINAHL, Embase and CENTRAL were searched for randomised controlled trials comparing Withania somnifera to any comparator, in people of any age, with any mental disorder. The meta-analyses were based on standardised mean differences (SMDs) and odds ratios with 95% confidence intervals, estimated through frequentist and Bayesian-hierarchical models with random-effects. Results Fourteen studies, corresponding to 360 people treated with Withania somnifera and 353 controls were included. Anxiety disorders were the predominant diagnostic category. Thirteen trials administered Withania somnifera orally (median dose 600 mg/day), one with Shirodhara therapy. The median follow-up time was 8 weeks. Although limited by the small number of studies, substantial between-study heterogeneity, and outlier effects, our investigation showed Withania somnifera effectiveness in improving anxiety (outlier-corrected SMD: -1.13 (95% CI: -1.65; -0.60), pooled SMD: -1.962 (95% CI: -2.66; -0.57)), depression (SMD: -1.28 (95% CI: -2.40; -0.16) and stress (SMD: -0.95 (95% CI: -1.46; -0.43) symptoms and sleep quality (SMD: -1.35 (95% CI: -1.79; -0.91). The effect size was confirmed using the Bayesian for anxiety but not for depression. No significant difference between Withania somnifera and the comparators was found for safety and tolerability. Conclusions We found evidence supporting the effectiveness of Withania somnifera in treating anxiety symptoms. Future trials should replicate this finding in larger samples and further clarify a possible Withania somnifera role in depression and insomnia treatment.