Ashwagandha Benefits: What the Research Shows About Sleep and Stress
Published on 21 September, 2026
Ashwagandha is the most studied herb in Ayurveda, and the strongest human evidence behind it is for sleep and for stress. If you are sleeping badly and feeling worn down, that is a reasonable reason to consider it, and there are trials to point to rather than tradition alone.
It is also a herb with real cautions attached. Some people should not take it at all, and there is a documented, uncommon association with liver injury that anyone starting it should recognize. None of that makes ashwagandha a bad choice. It makes it a supplement worth taking properly rather than casually.
What Ashwagandha Is
Ashwagandha is an extract of the root of Withania somnifera, an evergreen shrub found in parts of India, Africa and the Middle East. The Sanskrit name refers to the smell of a horse, which describes the fresh root accurately. It is sometimes sold as Indian ginseng, though it is unrelated to true ginseng.
In Ayurveda it is classed as a rasayana, a rejuvenative tonic, and has been used for centuries for fatigue, weakness and stress. It is the most frequently used Ayurvedic medicine today.
The root contains more than a hundred compounds. The group most often credited with its effects are the withanolides, a class of steroidal lactones, and most standardized extracts are sold on the basis of their withanolide content. Ashwagandha is generally described as an adaptogen, meaning a substance said to help the body cope with stress. That is a useful shorthand rather than a precisely defined pharmacological category.
What the Evidence Supports
Many clinical trials have looked at ashwagandha. The National Center for Complementary and Integrative Health (NCCIH), part of the US National Institutes of Health (NIH), notes that most have been small and have used a variety of different preparations, which makes them difficult to compare. Within that limitation, the picture is reasonably clear about where the support is strongest.
Sleep, where the evidence is best
A systematic review and meta-analysis published in the journal PLOS ONE in 2021 pooled five randomized controlled trials covering 400 participants. It found a small but statistically significant improvement in overall sleep, with a standardized mean difference of -0.59. Three details from that analysis are practical:
- The effect was more pronounced in people actually diagnosed with insomnia than in general populations sleeping reasonably well.
- Doses of 600 mg per day or more performed better than lower doses.
- Trials running eight weeks or longer showed more benefit than shorter ones.
In other words, ashwagandha appears to help sleep most in the people with the most trouble sleeping, at a meaningful dose, given enough time. The same review recorded improvements in mental alertness on waking and in anxiety scores, and found no effect on overall quality of life. Its authors were explicit that long-term safety data remain limited.
Stress and cortisol
NCCIH's assessment is that some ashwagandha preparations may be effective for stress. A 2023 systematic review in Nutrients looked specifically at cortisol, the hormone most associated with the stress response, and found that supplementation lowered cortisol across nine trials running between 30 and 112 days, without significant adverse effects reported. The authors noted that none of those studies examined what a sustained reduction in cortisol does to adrenal function over time, and recommended that ashwagandha be used under medical supervision for that reason.
A larger dose-response meta-analysis published in Complementary Therapies in Medicine in 2026 pooled 22 trials and reported improvements in stress, anxiety and depression scores. The direction was consistent, but the pooled effect sizes varied enormously between studies, and the authors concluded that well-designed high-quality trials are still needed before the findings translate into clinical recommendations. The honest summary across all of this work is that ashwagandha seems to reduce measures of stress in stressed people over a few weeks to a few months, and the size of that effect is not yet settled.
Anxiety, where the evidence is mixed
Despite anxiety being one of the most common reasons people try ashwagandha, NCCIH describes the evidence for it as unclear. Individual trials have reported improvements, several meta-analyses have found benefit, and yet the results are inconsistent enough across differing preparations and populations that no firm conclusion has been reached. If anxiety is your main concern, ashwagandha is reasonable to try but should not be the only thing you do.
Testosterone and sperm quality
There is limited evidence that taking ashwagandha for 2-4 months may raise testosterone levels and improve sperm quality in men. This is a smaller body of work than the sleep research, and the word NCCIH uses is limited.
Where the evidence does not yet support it
NCCIH states there is not enough evidence to determine whether ashwagandha helps with asthma, athletic performance, cognitive function, diabetes, menopause or female infertility. If you have seen ashwagandha promoted for any of these, the studies behind those claims are not yet strong enough to rely on.
Dosage and How to Take It
The trials that showed benefit generally used standardized root extracts rather than raw powder, at doses in the range where results appeared.
| Question | What the trials suggest |
|---|---|
| Typical dose | 600 mg per day of a standardized root extract performed better than lower doses in sleep research. Trial doses commonly range from 300 to 600 mg daily. |
| Form | Standardized extracts stating their withanolide content. Traditional churna, the raw powdered root, is used differently and at different quantities. |
| How long | Eight weeks or more before judging the effect. Benefits in trials built gradually rather than appearing immediately. |
| Timing | Evening suits people taking it for sleep. Split morning and evening doses are also used. It can cause drowsiness, so check how it affects you before starting a planned course. |
| With food | Taking it with food reduces the stomach upset some people experience. |
| Duration | NCCIH considers it possibly safe short term, up to about three months. There is not enough information to draw conclusions about longer use. |
That last point is the one most often overlooked. Ashwagandha is widely taken indefinitely, but the safety evidence supporting that has not been established. Taking it for a defined period, seeing whether it helps, and then reassessing with your clinician is a more defensible approach than adding it permanently to a daily stack.
Who Should Not Take Ashwagandha
This list matters more than the dosage table. NCCIH advises against ashwagandha in the following situations:
- Pregnancy. Ashwagandha should be avoided during pregnancy.
- Breastfeeding. It should not be used while breastfeeding.
- Before surgery. It is not recommended for people about to have an operation.
- Autoimmune conditions. Not recommended, as it may stimulate immune activity.
- Thyroid disorders. Not recommended. Ashwagandha can raise thyroid hormone levels, which matters if you have a thyroid condition or take thyroid medication.
- Existing liver disease. Ashwagandha should be avoided by people with cirrhosis or advanced chronic liver disease.
There is also evidence that ashwagandha interacts with several categories of medication, including drugs for diabetes and high blood pressure, immunosuppressants, sedatives, anticonvulsants and thyroid hormone. If you take any prescription medicine, this is a conversation to have with your pharmacist or physician before you start rather than after.
The Liver Question, Explained Properly
Ashwagandha has a good overall safety record and most people who take it have no trouble. Reported side effects are usually mild: drowsiness, stomach upset, diarrhea and nausea, the last of these more likely at larger doses.
Alongside that, cases of clinically apparent liver injury linked to ashwagandha products have been reported since 2017 and have increased in number since. LiverTox, the NIH database of drug-induced liver injury, now assigns ashwagandha a likelihood score of B, meaning a likely cause of clinically apparent liver injury. The pattern described there is specific enough to be useful:
- Injury has typically appeared two to twelve weeks after starting, not immediately.
- It usually presents with jaundice and itching, in a cholestatic or mixed pattern.
- In most cases it resolved within 1-4 months of stopping the product, though the jaundice was often prolonged.
- Rare cases of liver failure requiring transplant, and rare deaths, have occurred, particularly in people who already had cirrhosis or advanced liver disease.
- Restarting the same product after a reaction should be avoided.
Some reported cases involved multi-ingredient herbal products where contamination or mislabeling could not be excluded. In several cases, however, the product was tested and found to contain ashwagandha with no other contaminant.
Put in proportion: this is uncommon relative to how many people take ashwagandha, and it should not stop most healthy adults from trying it. What it should do is make you aware of the signs. Stop taking it and contact a doctor if you develop yellowing of the skin or eyes, dark urine, pale stools, persistent itching, pain under the right ribs, or unusual and lasting fatigue. Recognizing that early is what separates a reversible problem from a serious one.
Choosing a Product
Because supplements are not approved by the US Food and Drug Administration (FDA) before sale, what is in the bottle is the buyer's responsibility. Two things are worth checking.
The first is contamination. Some Ayurvedic preparations include metals and minerals by design, and the FDA warns that the presence of metals in some Ayurvedic products makes them potentially harmful. In testing referenced by NCCIH, about one in four Ayurvedic supplements had high levels of lead and almost half had high levels of mercury, and a 2015 survey of people using them found 40 percent with elevated blood lead. This is an argument for buying single-ingredient ashwagandha extract from a manufacturer that publishes third-party testing for heavy metals, rather than a compounded multi-herb formula of unclear origin.
The second is standardization. A label that states the withanolide percentage tells you something about what you are taking. One that says only ashwagandha does not.
It is also worth knowing that there is no significant regulation of Ayurvedic practice or education in the United States, and no state requires a practitioner to be licensed. If you want Ayurvedic guidance, look into the training of the person giving it.
What Else Helps With Stress and Sleep
Ashwagandha works best as one part of something larger, and the other parts are free.
- Consistent wake time. Getting up at the same hour every day, including weekends, does more for sleep quality than most interventions and costs nothing.
- Slow breathing. Extending the exhale relative to the inhale shifts the nervous system toward its rested state, and brief daily practice has been studied for mood and arousal.
- Daylight in the morning. Light exposure early in the day anchors the body clock and tends to improve sleep the following night.
- Movement. Regular physical activity has better evidence for both stress and mood than any supplement.
- Limiting caffeine after midday. Caffeine's half-life means an afternoon coffee is still active at bedtime for many people.
If your sleep or stress has been poor for months rather than weeks, that is worth investigating properly rather than managing with a supplement. Persistent insomnia, ongoing anxiety and low mood all have effective treatments, and a herb is not a substitute for finding out what is driving them.
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FAQs
Q: How long does ashwagandha take to work?
A: Longer than most people expect. In sleep trials, benefits were more evident in studies running eight weeks or more, and effects built gradually rather than appearing in the first few days. Give it at least 8 weeks at a consistent dose before deciding whether it is helping.
Q: What is the best time of day to take ashwagandha?
A: Evening suits most people taking it for sleep, since it can cause drowsiness. Some trials used split morning and evening doses. Taking it with food reduces stomach upset. Start it on a day when you can see how it affects you before you need to drive or work.
Q: Is it safe to take ashwagandha every day long term?
A: NCCIH considers it possibly safe for short-term use of up to about three months, and states there is not enough information to reach conclusions about long-term safety. Taking it for a defined period and then reassessing with your clinician is more defensible than taking it indefinitely.
Q: Does ashwagandha damage the liver?
A: For most people it does not, but clinically apparent liver injury has been reported and the NIH LiverTox database rates ashwagandha as a likely cause of it. Cases typically appeared 2-12 weeks after starting and usually resolved within 1-4 months of stopping. Anyone with cirrhosis or advanced liver disease should avoid it, and everyone else should stop and see a doctor if they notice jaundice, dark urine, persistent itching or unusual fatigue.
Q: Can I take ashwagandha with my thyroid medication?
A: Not without medical advice. Ashwagandha can raise thyroid hormone levels and NCCIH does not recommend it for people with thyroid disorders. It is also listed as interacting with thyroid hormone medication. Speak to the clinician managing your thyroid first.
Q: Does ashwagandha help with anxiety?
A: The evidence is genuinely mixed. Some trials and reviews report improvement, but NCCIH describes the overall evidence for anxiety as unclear, largely because studies used different preparations and populations. It is reasonable to try, but it should sit alongside other approaches rather than replace them.
Q: Ashwagandha or magnesium for sleep?
A: They are different tools. Ashwagandha has direct trial evidence in adults with insomnia at 600 mg or more over eight weeks. Magnesium is more relevant if your intake is low. Neither addresses an irregular sleep schedule, evening light or late caffeine, which are usually the bigger levers.
Q: Can women take ashwagandha?
A: Yes, outside pregnancy and breastfeeding, where it should be avoided. Much of the testosterone and fertility research has been in men, but the sleep and stress research has included women. The same cautions about thyroid conditions, autoimmune conditions and liver disease apply.
Q: What is the difference between ashwagandha root extract and churna?
A: Churna is the traditional raw powdered root, taken in larger quantities and often with milk or ghee. Standardized root extract concentrates the active compounds and is what almost all clinical trials have used. Doses are not interchangeable between the two.
Q: Should I cycle ashwagandha?
A: There is no trial evidence establishing an optimal cycling pattern. What the safety guidance supports is not treating it as a permanent daily supplement without review, given that long-term safety has not been characterized. A defined course followed by reassessment is a reasonable approach.
Q: Can ashwagandha be taken with antidepressants or sedatives?
A: Ashwagandha is listed as interacting with sedatives and with several other medication classes, and it may add to drowsiness. If you take any psychiatric medication, check with your prescriber before starting it and do not stop prescribed treatment in order to try a supplement.
Sources
- National Center for Complementary and Integrative Health, National Institutes of Health. Ashwagandha. nccih.nih.gov/health/ashwagandha
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Ashwagandha. National Institute of Diabetes and Digestive and Kidney Diseases. NBK548536.
- 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. PMID 34559859.
- Della Porta M, Maier JA, Cazzola R. Effects of Withania somnifera on Cortisol Levels in Stressed Human Subjects: A Systematic Review. Nutrients. 2023. PMID 38140274.
- Alsanie SA, Alhodieb FS, Askarpour M. Effects of ashwagandha (Withania somnifera) on mental health in adults: A systematic review and dose-response meta-analysis of randomized controlled trials. Complementary Therapies in Medicine. 2026. PMID 41644067.
- Akhgarjand C, 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. Phytotherapy Research. 2022. PMID 36017529.
- National Center for Complementary and Integrative Health. Ayurvedic Medicine: In Depth. nccih.nih.gov/health/ayurvedic-medicine-in-depth
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