Multiple systematic reviews and meta-analyses confirm ashwagandha’s ability to significantly reduce circulating cortisol. A 2025 systematic review across 15 RCTs (873 participants) published in BJPsych Open found statistically significant reductions in both cortisol and scores on the Hamilton Anxiety Rating Scale (HAM-A). A separate 2025 meta-analysis found a mean cortisol reduction of approximately −1.16 µg/dL (95% CI: −1.64 to −0.69, p < 0.001).
A foundational double-blind RCT (Chandrasekhar et al., 2012, Indian Journal of Psychological Medicine) showed that 300 mg twice daily for 60 days produced substantial reductions in cortisol alongside significant improvements on stress and anxiety assessment scales compared to placebo.
Beyond the biological cortisol marker, most trials show significant improvements on psychological stress scales. A meta-analysis in Explore (9 RCTs, 558 patients) found significant improvements on the Perceived Stress Scale (PSS), Hamilton Anxiety Scale, and serum cortisol. However, at least one 2025 meta-analysis found no significant effect on PSS, suggesting biological cortisol reduction does not always translate to subjective stress relief across all populations or study durations.
Ashwagandha is associated with improved sleep quality, duration, and disturbances in multiple trials. The proposed mechanisms include GABAergic activity (similar to benzodiazepine pathways) and reduced evening cortisol levels that facilitate deeper sleep. Examine.com summarizes consistent improvements in sleep across doses of 120–1,250 mg/day (most commonly 600 mg/day) for 4–12 weeks.
The evidence-based dose is 300–600 mg/day of a standardized root extract. Well-studied commercial formulations include KSM-66 and Sensoril. Ashwagandha is generally well tolerated; adverse effects in trials are mild and infrequent (primarily GI discomfort). Long-term safety data beyond 3 months is limited. Caution is warranted for individuals on thyroid medications or immunosuppressants, and use during pregnancy is not recommended.