Ashwagandha: a real signal for stress, and a real liver caveat

Ashwagandha (Withania somnifera) is the adaptogen with the most credible case behind it — which is faint praise in a category built largely on tradition and mechanism, but it’s genuinely one of the better-studied herbs for stress. Multiple small randomized trials point in the same direction: over a couple of months, standardized extracts seem to reduce self-reported stress and anxiety and lower cortisol. That consistency is worth something.

But this entry earns its moderate risk rating honestly, and it’s the part most product pages skip. Ashwagandha has been linked to rare cases of clinically apparent liver injury — occasionally severe enough to require a transplant. That doesn’t make it dangerous for most people, but it does mean this isn’t a supplement to shrug at, and it belongs nowhere near anyone with existing liver disease or a pregnancy.

What it seems to do

Ashwagandha is described as an adaptogen — a loosely-defined category meant to describe substances that blunt the body’s stress response. The most-measured biological effect is a reduction in cortisol, the primary stress hormone, alongside improvements on validated anxiety and stress questionnaires. Some trials also report better sleep, and a smaller literature suggests modest strength, recovery, or testosterone effects in men, though those are less consistent and shouldn’t be the reason you reach for it. The mechanism plausibly involves modulation of the HPA (hypothalamic-pituitary-adrenal, i.e. stress) axis, but the outcome data, not the mechanism, are what justify taking it seriously — and even those data come with real limits.

What the evidence shows

A 2025 systematic review and meta-analysis pooled 15 randomized trials in roughly 873 adults and found statistically significant reductions in anxiety, perceived stress, and cortisol at around 8 weeks. A frequently-cited earlier RCT gave 64 chronically-stressed adults 300 mg of a KSM-66 extract twice daily and reported large drops in stress scores and a ~28% reduction in serum cortisol versus placebo, with good tolerability in-trial.

Two honest caveats keep this at grade C. First, the trials are small, short, and heavily concentrated on a couple of branded, standardized extracts — KSM-66 and Sensoril — with frequent involvement from the companies that sell them. That’s not automatically disqualifying, but industry-funded supplement trials reliably skew toward positive results, and the reported effect sizes on some scales (double-digit percentage drops) are large enough to invite skepticism. Second, “reduces a cortisol number and a questionnaire score over 8 weeks” is not the same as “improves your health or your life over years,” which no one has demonstrated. The direction of effect is believable and reasonably consistent; the magnitude and durability are not settled.

The safety signal you shouldn’t skip

NIH’s LiverTox database classifies ashwagandha as a probable cause of clinically apparent liver injury. The pattern is fairly specific: a cholestatic or mixed injury with jaundice and itching, typically appearing 2 to 12 weeks after starting, in people taking commercial products. Most recover after stopping, but rare cases have been severe, including liver failure requiring transplantation — more likely in those with pre-existing liver disease. Injury has occurred even with products labeled as pure ashwagandha, so this isn’t purely a contamination story.

Practical implications:

• Avoid entirely if you have liver disease, or if you’re pregnant or breastfeeding (traditional caution plus limited safety data — some sources flag miscarriage risk).
• Use a defined trial — for example 4–8 weeks — rather than open-ended daily use.
• Stop immediately and seek care for fatigue, nausea, dark urine, itching, or yellowing of skin/eyes.
• Be cautious if you take thyroid medication (it may raise thyroid hormone levels) or sedatives.

The honest bottom line

For a healthy adult with situational stress, ashwagandha is a reasonable, time-limited experiment with a real if modest evidence base — better supported than most things in its category. But it is a pharmacologically active herb with a documented, if uncommon, liver risk, and that’s the trade the label won’t tell you. Treat it like a short trial with an off-ramp, not a daily habit you never revisit.