Effect of Ashwagandha Root Extract on Stress and Anxiety

A root used in Indian medicine for 3,000 years is now showing up in peer-reviewed journals — and the cortisol numbers are hard to ignore.

Quick Take

Multiple meta-analyses show ashwagandha significantly cuts anxiety scores, perceived stress, and cortisol levels compared to placebo.
One double-blind trial found anxiety dropped 41% in the ashwagandha group versus 24% in the placebo group.
An international psychiatric task force now provisionally recommends 300 to 600 mg daily for generalized anxiety disorder.
Long-term safety beyond three months is still unknown, and people with liver or thyroid conditions face real risks.

An Ancient Herb With a Surprisingly Modern Evidence Trail

Ashwagandha is not a wellness trend invented by an influencer. The root of the plant Withania somnifera has been used in Ayurvedic medicine for thousands of years. What is new is the clinical data. Researchers have now run multiple randomized, double-blind, placebo-controlled trials on it — the gold standard in medical research — and the results keep pointing the same direction. That consistency is what makes this story worth paying attention to.

The herb works by targeting the hypothalamic-pituitary-adrenal axis, which is the body’s central stress-response system. Clinical trials show it can lower cortisol levels in stressed adults by 23 to 33 percent. ^[3] Cortisol is the hormone your body floods your system with when you feel threatened. Chronically high cortisol is linked to poor sleep, weight gain, weakened immunity, and anxiety. Bringing it down with a root extract sounds almost too simple — but the data keeps showing it works.

What the Meta-Analyses Actually Found

A 2024 meta-analysis published in BJPsych Open found that ashwagandha significantly reduced anxiety scores on the Hamilton Anxiety Rating Scale, cut perceived stress scores, and lowered cortisol levels at eight weeks of treatment — all compared to placebo. ^[1] A separate meta-analysis of nine studies covering 558 participants found the same pattern: meaningful drops in stress, anxiety, and serum cortisol. ^[2] When two independent research teams pool different studies and land in the same place, that is not noise. That is signal.

One 60-day double-blind trial is especially telling. Participants taking ashwagandha saw anxiety fall by 41 percent. Those on placebo saw a 24 percent drop. ^[4] The placebo effect is real and powerful — so the gap between those two numbers matters. A separate 60-day trial tracked cortisol directly. The ashwagandha group saw a 27.9 percent reduction from baseline. The placebo group saw just 7.9 percent. ^[13] These are not tiny differences buried in statistical noise. They are clinically meaningful gaps.

The Dose and Timing That Seem to Work Best

Studies used daily doses ranging from 125 mg to 600 mg. The strongest benefits showed up at 300 to 600 mg per day. ^[5] The World Federation of Societies of Biological Psychiatry and the Canadian Network for Mood and Anxiety Treatments jointly issued a provisional recommendation for 300 to 600 mg of standardized root extract daily for generalized anxiety disorder. ^[5] Most people start noticing something within two weeks, but the full benefit builds over six to ten weeks. ^[3] Patience is part of the protocol.

4. Ashwagandha KSM-66 (cortisol reducer):

decreases the stress hormone cortisol, which decreases testosterone. Take 300–600 mg per day (KSM-66 is the finest form).

According to studies, testosterone levels grow significantly within 60 days. Increased energy, less anxiety, and…

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The Mayo Clinic notes that the best products are standardized to a specific percentage of withanolides — the active compounds — typically between 0.3 and 1.5 percent, with doses ideally containing at least 6 mg of withanolides. ^[8] That detail matters because the supplement market is full of products with inconsistent potency. Buying a cheap, unstandardized product and expecting the results from clinical trials is like comparing store-brand aspirin to a precisely dosed pharmaceutical. The label details are not marketing fluff — they affect whether the thing actually works.

The Real Risks You Should Not Skip Over

The National Institutes of Health (NIH) is direct about the limits here: ashwagandha appears well tolerated for up to about three months, but long-term safety data is simply missing. ^[5] Most trials were small and ran only six to eight weeks. That is enough to see a stress signal, but not enough to know what happens to your liver or thyroid after a year of daily use. The European Food Safety Authority has not approved any health claims for ashwagandha because it considers the current evidence insufficient. ^[9] That is a reasonable institutional caution, not a dismissal of the science.

People with pre-existing liver conditions, thyroid disorders, or those taking sedative medications face real and specific risks. ^[10] Ashwagandha may also cause excessive sedation when combined with anti-anxiety drugs. Pregnant women should avoid it entirely, as it may cause miscarriage. ^[3] Common mild side effects include stomach upset, loose stools, nausea, and drowsiness. ^[5] None of that makes ashwagandha dangerous for most healthy adults. But it does mean this is not a supplement you toss in your cart without reading the fine print first.

The Bottom Line on a 3,000-Year-Old Remedy

The science on ashwagandha is more solid than most supplements get. Multiple independent meta-analyses, double-blind trials, and now a provisional recommendation from an international psychiatric task force — that is a meaningful evidence stack. The honest caveat is that most studies are short, and nobody knows what happens with years of use. For a healthy adult dealing with chronic stress and poor sleep, the risk-to-benefit math looks favorable at 300 to 600 mg of a standardized extract for up to three months. After that, talk to your doctor. The herb has earned a serious conversation — just not blind faith.