Ashwagandha: The Cortisol Evidence and the Liver Warning

Ashwagandha has had the kind of year that makes an editorial team suspicious on principle: search interest climbing, bottles appearing in every supplement aisle, and a marketing story — "ancient herb, modern stress" — that is compelling enough to not ask what was actually measured in a lab.

This article covers what was actually measured, in the trial most of that marketing leans on; why "lowers stress" and "gives you energy" are not the same finding, even when they get sold as one; the testosterone question, covered more fully elsewhere on this site; and a safety signal — a real, if rare, link to liver injury — that most of the marketing skips entirely.

What ashwagandha actually is

Ashwagandha (Withania somnifera) is a plant used in traditional Ayurvedic medicine, also known as Indian ginseng. The National Center for Complementary and Integrative Health (NCCIH) notes it is commonly promoted for stress and anxiety, sleep, male infertility and athletic performance.

Many clinical trials have looked at ashwagandha, per NCCIH, but most have had small sample sizes and used a variety of different preparations — which matters more than it sounds, because a result from one specific extract at one specific dose does not automatically transfer to a different product on a different shelf.

The trial that built its reputation

A 2012 randomized, double-blind, placebo-controlled trial enrolled 64 adults with a history of chronic stress. Half took 300mg of a high-concentration ashwagandha root extract twice daily — 600mg total — and half took placebo, for 60 days.

The same trial found similarly large, statistically significant improvements on two other standard stress-assessment scales, the General Health Questionnaire-28 and the Depression Anxiety Stress Scale. Adverse events were mild and similarly common in both groups — nasal congestion, constipation, cough and cold, drowsiness and decreased appetite in the ashwagandha group, nothing the authors linked to a known mechanism of the drug.

This is one well-conducted trial with a modest sample, not a settled finding from dozens of large studies. It is also, honestly, the trial behind most of the specific numbers you will see quoted elsewhere — which is worth knowing before treating any single percentage as gospel.

Why "less stressed" and "more energy" aren't the same claim

NCCIH's own summary of the evidence is narrower than most marketing: research shows some ashwagandha preparations may be effective for insomnia and stress, while evidence is unclear about its effects on anxiety specifically. There is no mention of daytime energy or vitality as its own measured outcome — because the trials, including the one above, were not designed to measure it.

That distinction matters for this site's whole Energy section. A herb that genuinely lowers cortisol and improves sleep could plausibly leave a chronically stressed man feeling less depleted during the day — but that is an indirect, downstream effect, not the same thing as a direct energy boost, and it is a different mechanism than the one this site's caffeine article describes, where most of the day-to-day lift turns out to be withdrawal relief rather than a true boost above baseline either. Two different supplements, two different reasons the "more energy" story oversells what was actually tested.

The sleep evidence, more cautiously stated

Sleep is the one area besides stress where NCCIH is willing to say "may be effective" rather than "unclear." Among its cited references is a 2021 systematic review and meta-analysis specifically on ashwagandha and sleep — included in NCCIH's reference list as part of the evidence behind that conclusion, though this site has not independently read the full study and is relying on NCCIH's summary judgment of it, not quoting its numbers directly.

If sleep itself, rather than a supplement for it, is the actual problem, this site's sleep section covers the full range of causes and treatments in more depth than any single herb article can.

The testosterone question, covered elsewhere

NCCIH notes there is some limited evidence that taking ashwagandha for 2 to 4 months may increase testosterone levels and sperm quality. This site covers that specific question in real depth — four separate human trials, including the one that found no effect in stressed men specifically — in testosterone booster supplements: what each one does. Repeating that analysis here would just be the same evidence twice; this article's job is the stress, sleep and safety side of the same herb.

The liver warning most marketing doesn't mention

This is the part a lot of ashwagandha content skips entirely, and it is not a fringe concern. NCCIH states it plainly: although it is rare, there have been a number of cases that link liver injury to ashwagandha supplements. The Netherlands' national pharmacovigilance center, Lareb, put a number on part of that signal — after an initial 2023 warning, it received eight new reports of suspected liver toxicity linked to ashwagandha products in the time since, and stated plainly that although liver toxicity with ashwagandha-containing products appears to be rare, it is important to be aware of the risk.

Lareb is also honest about a specific limitation: herbal products often contain more than one herb, and sometimes contain ingredients not listed on the label, or are contaminated — so for any individual report, it cannot be ruled out that something else in the product, not the ashwagandha itself, caused the liver injury. That is not the same as the risk being imaginary — it is a real, accumulating signal that simply has not been nailed down to a precise rate yet.

NCCIH's broader safety read: ashwagandha may be safe when taken short-term, up to about three months, the same window covered in most of the positive trials. There is not enough information to draw conclusions about longer use either way — which cuts against treating it as a supplement to take indefinitely just because a 60-day trial went well.

Who should avoid it, or be cautious

NCCIH is specific here, and some of it applies directly to this site's own readers. Avoid it during pregnancy or breastfeeding, before surgery, and if you have an autoimmune or thyroid disorder. Because ashwagandha may increase testosterone, NCCIH states that people with hormone-sensitive prostate cancer should avoid its use — a direct, specific caution for exactly the kind of reader who already has a prostate-cancer history and might otherwise reach for it as a harmless stress supplement.

NCCIH also lists real drug interactions: medicines for diabetes and high blood pressure, immunosuppressants, sedatives, anti-seizure medications and thyroid hormone medication. None of this makes ashwagandha dangerous for most healthy men taking it short-term — it makes it a supplement worth mentioning to a doctor or pharmacist before starting, the same way any new medication would be, rather than something to add quietly because a friend recommended it.

What this actually means for you

1. Know which claim you're testing. The trial evidence is strongest for stress and cortisol, with sleep a step behind and daytime energy not directly measured at all. Decide which problem you're actually trying to solve before buying a bottle.
2. Match the dose and duration to what was actually studied. The clearest positive trial used 600mg a day, split into two doses, for 60 days — not a single capsule taken once and judged the next morning.
3. Treat three months as the edge of what's known to be reasonably safe. Beyond that window, per NCCIH, the safety data simply runs out.
4. Check the exclusion list against your own situation first. Pregnancy, upcoming surgery, autoimmune or thyroid disease, hormone-sensitive prostate cancer, and the specific medication classes above are reasons to ask a doctor before starting, not reasons to assume it is automatically off the table.
5. If it's raised testosterone you're actually after, read the fuller, four-trial picture in testosterone booster supplements before deciding ashwagandha is the ingredient that gets you there.