Claim deep dive·Moderate evidence·Updated July 13, 2026
Evidence review: Ashwagandha reduces serum cortisol
Multiple RCTs show measurable cortisol reduction at 300 to 600 mg/day of standardized root extract over 4 to 8 weeks.
The bottom line.
The strongest studies.
Sorted by study tier (meta-analyses first, then RCTs, then reviews) and recency. Every entry links to PubMed by PMID, and every citation on this page points here.
Meta-analyses & systematic reviews
1- 1Effects of Withania somnifera on Cortisol Levels in Stressed Human Subjects: A Systematic ReviewSource linkedPMIDDella Porta M, Maier JA, Cazzola R · Nutrients · 2023
Randomized controlled trials
2- 2A standardized Ashwagandha root extract alleviates stress, anxiety, and improves quality of life in healthy adults by modulating stress hormones: Results from a randomized, double-blind, placebo-controlled study.Source linkedPMIDMajeed M, Nagabhushanam K, Mundkur L · Medicine · 2023
Standardized ashwagandha root extract significantly reduced cortisol levels and perceived stress while improving quality of life scores in healthy adults.
- 3A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adultsSource linkedPMIDChandrasekhar K et al. · Indian J Psychol Med · 2012
300 mg twice daily for 60 days significantly reduced serum cortisol levels compared to placebo
What pushes back.
Caveats, null findings, and methodological limits that hold the tier where it is.
What the evidence supports.
What we recommend
300 to 600 mg/day of a standardized root extract (KSM-66 or Sensoril) for 4 to 12 weeks. Cycle off periodically; long-term hormonal effects are under-studied.
Tier criteria: /methodology/evidence-tiers. Sourcing standards: /methodology/interactions.
Common questions.
Quick answers drawn from the verdict, evidence, and recommendation above.
Does the evidence support the claim that ashwagandha reduces serum cortisol?
Multiple RCTs show measurable cortisol reduction at 300 to 600 mg/day of standardized root extract over 4 to 8 weeks.
How strong is the evidence behind Ashwagandha for this claim?
NutriStack rates this as Moderate evidence, meaning several aligned RCTs or one large RCT plus supporting reviews. Full tier criteria are at https://nutristackapp.com/methodology/evidence-tiers.
What contrary evidence or caveats apply?
Most trials are 8 weeks or shorter. Effect on cortisol does not consistently translate to clinical depression or anxiety outcomes. Rare but real hepatotoxicity has been reported.
What does NutriStack recommend?
300 to 600 mg/day of a standardized root extract (KSM-66 or Sensoril) for 4 to 12 weeks. Cycle off periodically; long-term hormonal effects are under-studied.
Selected claims, opened up
This is how NutriStack presents an evidence review.
Each published claim review shows its verdict, attached studies, contrary evidence, dose context, and limits. Coverage is selective rather than a claim that every database assertion has received the same review.