Key takeaways
- Lopresti and Smith’s 2021 review in the Journal of Herbal Medicine gathered 41 human trials of ashwagandha across many conditions. Stress, anxiety, and sleep have the most support.
- For stress and anxiety, the NIH counts 7 trials in that review (491 adults, all in India, 6 to 8 weeks) that favored ashwagandha over placebo. NCCIH, another NIH center, still calls the anxiety evidence unclear.
- Fertility evidence is limited and mostly about men, and there is not enough evidence for women.
- Ashwagandha seems tolerated for up to about 3 months, but rare liver injury has been reported, and it is not advised in pregnancy or with thyroid conditions. Some European regulators have acted against it.
Ashwagandha may help some people feel less stressed and sleep a little better over 6 to 12 weeks, but the evidence is thinner than the marketing, and it is not suitable for everyone. For fertility, evidence is limited and mostly from studies in men. For wider mental health claims, the support is weaker still.
What the 2021 review is
Lopresti and Smith published the review in the Journal of Herbal Medicine in 2021. Following PRISMA reporting rules, it collected human trials in which ashwagandha was the only ingredient, used alone or as an add-on, for mental or physical conditions or performance. It found 41. A separate sleep meta-analysis describes the mix: seven of the 41 trials were on stress and anxiety, one on insomnia and one on general well-being, so most of the 41 are about other things.
A systematic review gathers and appraises trials. It cannot turn small, short, or differently designed studies into proof. The NIH Office of Dietary Supplements notes that studies used many different extracts and doses, which makes it hard to name a specific product or amount.
What was shown, and what was not
| Claim | Evidence | Limit |
| Lowers stress and anxiety scores | 7 trials in the review: 491 adults, all in India, 6 to 8 weeks, ashwagandha versus placebo. A 2025 meta-analysis found anxiety lower on the Hamilton scale at 8 weeks (pooled difference -3.52 points) and stress lower on the Perceived Stress Scale (-4.88). A 2024 meta-analysis of 9 trials and 558 people also favored ashwagandha | Small, short trials, mostly in India. I read only the meta-analysis abstracts. NCCIH calls the anxiety evidence unclear, and one 12-week trial in overweight adults with low energy found less fatigue but no drop in perceived stress |
| Lowers cortisol | Both meta-analyses reported lower cortisol than placebo | Cortisol is a lab marker, not how a person feels; results average across different products |
| Improves sleep | 5 trials, 372 adults, all in India, 6 to 12 weeks: a small but significant improvement, larger in people with insomnia, at 600 mg a day and after 8 weeks or more | Small effect, short trials |
| Raises testosterone and sperm quality in men | NCCIH: limited evidence that 2 to 4 months of use may raise both. A 2018 review found before-and-after gains in men with low sperm counts after 90 days (sperm concentration up 167%, semen volume 59%, motility 57%) | That review included only one randomized trial; the rest was before-and-after data. |
| Helps female fertility | NCCIH: not enough evidence | Not established |
| Treats depression or improves memory | NCCIH: not enough evidence for cognitive function and several other uses; I found no authoritative statement that it treats depression | Not established |
What the trials used. In the 7 stress and anxiety trials, doses ranged from 240 to 1,250 mg of extract per day, and in several, the benefit appeared larger at 500 to 600 mg per day. An international expert task force provisionally recommended 300 to 600 mg a day of a root extract standardized to 5% withanolides for generalized anxiety disorder in 2022. It said more data was needed for a stronger recommendation. This describes the research. It is not dosing advice.
Fertility: what is and is not known
The fertility claim rests mostly on men with low sperm counts. The 2018 review in Phytomedicine found only one randomized trial, so it did not pool randomized results. Its large percentage gains were measured against each man’s own starting point after 90 days. Without a placebo group, those gains cannot be separated from other causes. The NIH sources add that ashwagandha might raise testosterone, which is why experts advise against it for men with hormone-sensitive prostate cancer.
For women, NCCIH says there is not enough evidence on infertility, and it advises avoiding ashwagandha during pregnancy and breastfeeding. If you are trying to conceive, talk to a clinician before taking it.
Safety: who should be careful
- Short-term use looks tolerated. In trials, it was well tolerated for up to about 3 months. Common side effects were mild: stomach upset, loose stools, nausea, and drowsiness. Long-term safety is not known.
- Liver. The NIH’s LiverTox database rates ashwagandha as a likely cause of clinically apparent liver injury, though rare. Cases typically appeared 2 to 12 weeks after starting, with jaundice and itching, and most resolved within 1 to 4 months of stopping. A few fatal cases and liver transplants were reported, particularly in people with existing liver disease. LiverTox advises avoiding it in cirrhosis or advanced chronic liver disease. Many cases involved mixed or unverified products.
- Thyroid. Small studies and case reports suggest it can change thyroid hormone levels, and NCCIH does not recommend it for people with thyroid or autoimmune disorders.
- Pregnancy and breastfeeding. NCCIH advises avoiding it. The miscarriage concern is disputed: the American Herbal Pharmacopoeia says its own monograph was misrepresented and that there is no evidence it causes abortion. Regulators still advise caution.
- Medicines. It may interact with diabetes and blood pressure medicines, immunosuppressants, sedatives, anti-seizure medicines and thyroid hormone. NCCIH also advises against it before surgery.
What regulators have done
This changes quickly, so check each point on your publish date.
- Denmark banned ashwagandha in food supplements in 2023 after a safety assessment, and France’s food safety agency (ANSES) advised against it in 2024 for groups including pregnant and breastfeeding women and people with endocrine disorders, according to the NIH.
- In April 2026, India restricted ashwagandha products to root and root extracts and prohibited leaf. Trade press reported an interim court stay on the leaf ban in May 2026.
- The Netherlands. Trade press reported a ministry decision in early 2026 to ban it in supplements, and a June 2026 piece, sponsored by a supplement maker, said its status was unclear.
- United States. It is sold as a dietary supplement, which the FDA does not approve before sale.
What you can do today
If you are thinking about trying ashwagandha:
- Ask a doctor or pharmacist first if you take any medicine, have a liver, thyroid, or autoimmune condition, are pregnant, breastfeeding, or trying to conceive, or have surgery planned.
- Read the label. Trials used specific extracts, and products differ in the plant part used and their strength. Mixed products are harder to judge, and LiverTox notes that herbal mixtures are often mislabeled.
- Stop and get medical help if you notice yellow skin or eyes, itching, severe nausea, unusual tiredness or abdominal pain.
- Do not use it instead of care. For persistent anxiety, low mood, sleep problems, or difficulty conceiving, see a clinician. If you are in distress or thinking about harming yourself, contact your local emergency services or a crisis line right away.
- Consider other options studied for stress and mood, such as those in our guides to mindfulness and mental wellness and psychobiotics.
The bottom line
The 2021 review and the trials since point the same way: ashwagandha may modestly lower stress and improve sleep over 6 to 12 weeks, but the studies are small, short, and mostly from India. Fertility claims rest on thin, mostly uncontrolled data in men, and the broader mental health claims are not established. Safety is the part to take seriously, with rare liver injury, thyroid and pregnancy warnings, and regulators acting in several countries. Treat “proven” headlines with caution, and talk to a clinician before you start.
Related on Scientific Digest: Mindfulness and Mental Wellness: What the Research Shows and How to Start Safely · Psychobiotics and Mental Health: How Gut Bacteria Can Naturally Improve Mood and Reduce Stress
References & Further Reading:
Lopresti, A.L., Smith, S.J. (2021). Ashwagandha (Withania somnifera) for the treatment and enhancement of mental and physical conditions: A systematic review of human trials. Journal of Herbal Medicine, 28, 100434.
DOI: https://doi.org/10.1016/j.hermed.2021.100434
NIH Office of Dietary Supplements. Ashwagandha: Is it helpful for stress, anxiety, or sleep? Health Professional Fact Sheet. Updated 2 May 2025.
National Center for Complementary and Integrative Health. Ashwagandha: Usefulness and Safety. Last updated March 2023.
LiverTox. Ashwagandha. National Institute of Diabetes and Digestive and Kidney Diseases. Updated 3 December 2024.
Cheah KL, Norhayati MN, Husniati Yaacob L, Abdul Rahman R. Effect of ashwagandha (Withania somnifera) extract on sleep: a systematic review and meta-analysis. PLoS One. 2021;16:e0257843.