Ashwagandha and Cortisol: The Evidence

Ashwagandha (Withania somnifera) is an evergreen shrub used in Ayurvedic tradition as an adaptogen, standardized in supplement form to its active withanolides and studied mainly for its effect on the stress hormone cortisol. Of all the claims made for it, the cortisol one is the most testable: cortisol is a number you can measure in blood or saliva, so it’s the right place to look if you want to know whether the herb does anything measurable rather than just feels calming.

What follows is a plain evidence summary covering what the randomized trials actually reported, how large the cortisol reductions were, and, just as important, how good those studies really are. The honest answer is more interesting than either the hype or the dismissal.

Everything below is about supporting a healthy stress response, not treating anxiety, depression, or any diagnosed condition. Nothing here is medical advice. If stress is affecting your daily life, a clinician is the right first call. See our crisis and professional-support resources.

What cortisol is, and why ashwagandha is studied for it

Cortisol is the body’s main glucocorticoid stress hormone, released by the adrenal glands under the control of the hypothalamic-pituitary-adrenal (HPA) axis. It follows a daily rhythm (highest in the morning, tapering through the day) and rises in response to physical and psychological stress. That’s normal and useful. The problem is chronically elevated cortisol, which is associated with poor sleep, higher perceived stress, and metabolic strain.

Ashwagandha is classed as an adaptogen: a plant proposed to help the body maintain balance under stress. The leading hypothesis for its cortisol effect is modulation of the HPA axis, dampening the overactive stress response rather than blunting cortisol outright. The activity is usually attributed to steroidal lactones called withanolides, the compounds most standardized extracts are measured against. This is a plausible, lab-supported mechanism, but a mechanism is a reason to run trials, not a substitute for them.

What the research actually shows

The most useful thing to know is that ashwagandha’s cortisol effect has been tested in several randomized, double-blind, placebo-controlled trials (the strongest design available for this kind of question) and they broadly agree. Most of them used KSM-66, a full-spectrum standardized root extract, in chronically stressed but otherwise healthy adults.

The best-known result comes from a 2012 trial by Chandrasekhar and colleagues: 64 chronically stressed adults took 300 mg of KSM-66 twice daily (600 mg/day) or placebo for 60 days. The ashwagandha group showed a roughly 27.9% reduction in serum cortisol relative to placebo, alongside improvements on the Perceived Stress Scale. A 2017 trial by Choudhary and colleagues, in adults under chronic stress, reported a significant reduction in serum cortisol at the same dose. A 2019 study by Salve and colleagues tested both 250 mg and 600 mg per day and found significant morning-cortisol reductions at both, with the larger effect at the higher dose. A 2019 trial by Lopresti and colleagues, using 240 mg/day, reported a roughly 23% drop in morning cortisol versus placebo.

The RCTs at a glance

Year	Extract / dose	Population	Cortisol finding
2012	KSM-66, 600 mg/day	64 stressed adults	~27.9% lower serum cortisol vs placebo
2017	KSM-66, 600 mg/day	Adults under chronic stress	Significant serum cortisol reduction
2019	KSM-66, 250 & 600 mg/day	58 stressed adults	Significant morning-cortisol drop at both doses
2019	KSM-66, 240 mg/day	60 stressed adults	~23% lower morning cortisol vs placebo

Systematic reviews echo the trials. A 2014 systematic review concluded that ashwagandha showed benefit for anxiety and stress outcomes across the available human trials, and a 2022 systematic review and meta-analysis by Akhgarjand and colleagues found ashwagandha supplementation was associated with significant reductions in stress and anxiety scores. The direction of evidence is consistent, and that consistency is the strongest thing it has going for it.

The study-quality caveats (read this part)

Consistent isn’t the same as conclusive, and the cortisol literature has real limits worth stating plainly.

The trials are small and short. Most enrolled a few dozen people and ran for eight to twelve weeks. That’s enough to detect a within-study effect but not enough to tell you about durability, rare harms, or how well the result generalizes.

There’s also a funding and independence problem. A large share of the KSM-66 cortisol trials were sponsored by, or involved authors connected to, the extract’s manufacturer. Industry funding doesn’t automatically make a finding wrong, but it’s a well-documented source of bias toward positive results, and it means the evidence base is narrower than the raw study count suggests.

The research is also geographically concentrated, with many trials run by an overlapping set of investigators, and standardization varies between the extracts tested. Cortisol was often a secondary outcome measured at a single morning timepoint, which is a noisy way to capture a hormone with a strong daily rhythm.

On our evidence scale, this puts ashwagandha at Moderate: multiple randomized trials pointing the same way and supportive meta-analyses pull it up; small samples, short durations, manufacturer funding, and regional concentration keep it out of the well-studied top tier. That’s a genuinely respectable place for a botanical to sit, and we’d rather state it accurately than oversell it.

Typical use

Across the positive trials, the studied dose is a standardized root extract at 240–600 mg per day, most often KSM-66, with the 300 mg twice-daily (600 mg/day) schedule being the most tested. More does not appear to be better; there’s no evidence that pushing past 600 mg lowers cortisol further, and higher doses raise the odds of side effects like drowsiness or stomach upset.

The cortisol changes in the trials were measured at eight weeks, so treat ashwagandha as a daily supplement you take consistently and reassess after roughly two months, not a same-day calming aid. Many people take it with food; some prefer the evening dose given its mild sedating tendency, which is also why it’s sometimes used for sleep and evening wind-down. If you’d like to see the specific standardized extract we profile, our ashwagandha product hub lays out what to look for on a label.

What to look for in an ashwagandha supplement for cortisol

If the trial results are what drew you in, the sensible move is to buy something close to what those trials actually used rather than the cheapest capsule on the shelf. Start with the form: most of the cortisol research used KSM-66, a standardized full-spectrum root extract, so choosing that form buys you a known quantity at a studied dose. Check that the label states a withanolide percentage (the compounds extracts are measured against) and that the dose falls in the 240–600 mg per day range the studies tested; more is not better. Prefer a root-only extract over a root-and-leaf blend, since the leaf material was not part of the cortisol trials, and favour a product with third-party testing for purity. Our ashwagandha page profiles a specific standardized extract, and our stress support guide shows where it fits alongside other options. Buy on the stated form, standardization, and dose, not on the calming imagery on the box.

Cautions and who should be careful

Ashwagandha is generally well tolerated in the trials, with side effects usually mild (drowsiness, digestive upset). But “generally well tolerated” is not “fine for everyone,” and a few situations genuinely matter.

Pregnancy is the clearest contraindication: ashwagandha has a traditional reputation as an abortifacient and should not be used while pregnant. Thyroid conditions deserve caution because ashwagandha may raise thyroid hormone levels, which can be a problem if you have hyperthyroidism or take thyroid medication. Because it can nudge the immune system, people with autoimmune conditions (such as lupus, rheumatoid arthritis, or Hashimoto’s) should check with their clinician first.

Rare reports of liver injury have also been associated with ashwagandha supplements; stop and seek care if you notice jaundice, dark urine, or unusual fatigue. Ashwagandha can add to the effect of sedatives and may interact with thyroid, immunosuppressant, and blood-sugar or blood-pressure medications. If you take any prescription drug or manage a health condition, talk to your doctor before starting. For the bigger picture on building a stress-support routine, see our overview of the lifestyle foundations of mood support.

Supplements mentioned

• Ashwagandha (standardized root extract): the evergreen-shrub adaptogen covered above, studied at 240–600 mg/day for stress and cortisol support. Evidence tier: Moderate.

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This article is for general information and stress support only. It is not medical advice and does not diagnose, treat, or cure any condition. Read our full medical disclaimer, and speak with a qualified healthcare professional before starting any supplement, especially if you are pregnant, taking medication, or managing a health condition. If you are struggling, our get-help page lists where to turn.

Sources

1. Chandrasekhar K, Kapoor J, Anishetty S. A 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 adults. Indian J Psychol Med. 2012;34(3):255–262. doi:10.4103/0253-7176.106022
2. Choudhary D, Bhattacharyya S, Joshi K. Body Weight Management in Adults Under Chronic Stress Through Treatment With Ashwagandha Root Extract: A Double-Blind, Randomized, Placebo-Controlled Trial. J Evid Based Complementary Altern Med. 2017;22(1):96–106. doi:10.1177/2156587216641830
3. Salve J, Pate S, Debnath K, Langade D. Adaptogenic and Anxiolytic Effects of Ashwagandha Root Extract in Healthy Adults: A Double-blind, Randomized, Placebo-controlled Clinical Study. Cureus. 2019;11(12):e6466. doi:10.7759/cureus.6466
4. Lopresti AL, Smith SJ, Malvi H, Kodgule R. An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: A randomized, double-blind, placebo-controlled study. Medicine (Baltimore). 2019;98(37):e17186. doi:10.1097/MD.0000000000017186
5. Pratte MA, Nanavati KB, Young V, Morley CP. An alternative treatment for anxiety: a systematic review of human trial results reported for the Ayurvedic herb ashwagandha (Withania somnifera). J Altern Complement Med. 2014;20(12):901–908. doi:10.1089/acm.2014.0177
6. Akhgarjand C, Asoudeh F, Bagheri A, et al. Does Ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? A systematic review and meta-analysis of randomized controlled trials. Phytother Res. 2022;36(11):4115–4124. doi:10.1002/ptr.7598
7. Langade D, Kanchi S, Salve J, Debnath K, Ambegaokar D. Efficacy and Safety of Ashwagandha (Withania somnifera) Root Extract in Insomnia and Anxiety: A Double-blind, Randomized, Placebo-controlled Study. Cureus. 2019;11(9):e5797. doi:10.7759/cureus.5797