Ashwagandha for Stress and Sleep: What the Evidence Shows
Share
It is one in the morning and you are still awake. The day is over but your head has not caught up. You are tired and wired at the same time, running tomorrow's to-do list on a loop. Somewhere between a podcast advert and a friend's recommendation, one word keeps coming up as the calm, natural fix: ashwagandha.
The label sounds confident. Lower stress, deeper sleep, a steadier mind. The bottles are on every shelf in London and the sales keep climbing. What is harder to find is a straight answer on whether the research backs it and whether it is safe to take. This post gives the honest version, based on the trials rather than the marketing.
What ashwagandha actually is
Ashwagandha is a small shrub, Withania somnifera, used in Ayurvedic medicine for centuries. The part that ends up in supplements is usually the root, dried and concentrated into a standardised extract. It is often called an adaptogen, a loose term for a plant thought to help the body cope with stress. That word is marketing shorthand, not a medical category, so it is worth setting aside and looking at what the extract does in controlled trials.
Most quality research uses a standardised root extract with a set level of active compounds called withanolides. Two brand-name extracts, KSM-66 and Sensoril, appear in a lot of the studies. This matters because a cheap capsule of unstandardised powder is not the same product that was tested. When you read that ashwagandha helped in a trial, it usually means a specific, measured extract at a specific dose, not whatever happens to be in the tub.
What the stress research shows
The strongest recent evidence is a 2025 systematic review and meta-analysis in BJPsych Open by Bachour and colleagues. It pooled 15 randomised controlled trials with a combined 873 adults and looked at three outcomes: the stress hormone cortisol, self-reported stress, and anxiety.
Across those trials, ashwagandha lowered morning cortisol compared with placebo, with a pooled effect of minus 2.36 (95 percent confidence interval minus 3.26 to minus 1.46). Self-reported stress, measured with the Perceived Stress Scale, fell by an average of 4.88 points against placebo (confidence interval minus 7.84 to minus 1.91). Anxiety, measured on the Hamilton scale at eight weeks, dropped by 3.52 points (confidence interval minus 6.00 to minus 1.04). In plain terms, people taking the extract reported feeling less stressed and less anxious, and their cortisol, a marker of the stress response, moved in the same direction.
Two honest caveats sit alongside those numbers. The review found no improvement in overall quality of life, so this is a targeted effect on stress markers rather than a broad lift in wellbeing. And confidence intervals this wide tell you the size of the benefit varies a lot from person to person. The direction of the evidence is consistent and positive. The magnitude is modest and individual.
What it does for sleep
Sleep is the other reason people reach for ashwagandha, and here the evidence is smaller but points the same way. A 2021 meta-analysis in PLoS One by Cheah and colleagues combined 5 randomised trials in 400 adults. Overall, the extract produced a small but real improvement in sleep, a standardised effect of about 0.59 (confidence interval 0.42 to 0.75), which counts as a moderate benefit. A bigger number means a bigger improvement.
The more useful detail is in the subgroups. The benefit was clearer at doses of 600 mg a day or more, when the extract was taken for eight weeks or longer, and in people who actually had insomnia rather than healthy sleepers looking for a small edge. The chart below shows how the effect grew across those groups.
The takeaway is not that ashwagandha is a sleeping pill. It is that, given enough dose and enough time, it may take the edge off a stressed, restless mind and let sleep come more easily, with the biggest gains in people whose sleep is genuinely poor.
Sensible doses and how to take it
Most stress trials used 300 to 600 mg of a standardised root extract a day, often split into two doses. Sleep benefits showed up most clearly from 600 mg upward. A safety trial by Vaidya and colleagues in 2023 used 500 mg twice a day for four weeks in healthy volunteers with no adverse effects, so that range is well within what has been studied.
A few practical points from the research:
- Look for a standardised root extract on the label, ideally naming the withanolide content or a tested extract such as KSM-66 or Sensoril.
- Give it time. The stronger sleep and stress effects appeared after about eight weeks, not on the first night.
- Take it with food to reduce the chance of stomach upset, which is the most common mild complaint.
- If sleep is the goal, an evening dose makes sense. If stress is the goal, splitting it across the day is reasonable.
Who should be careful
This is the part the adverts skip, and it matters. In trials, ashwagandha is generally well tolerated, and the side effects that do appear are usually mild, such as drowsiness or stomach upset. The safety point that deserves real attention is the liver.
A few other groups should steer clear or check with a doctor first. Standard guidance is to avoid ashwagandha in pregnancy and breastfeeding, because safety has not been established. It can also nudge thyroid hormone levels. The Vaidya safety trial recorded a small rise in one thyroid marker that stayed within the normal range, so people with thyroid conditions or on thyroid medication should get advice first. It may add to the effect of sedatives and some anxiety or blood pressure medications, and it may not suit people with autoimmune conditions. If you take any regular medication, treat ashwagandha as a drug and ask your GP or pharmacist before you start.
One more point applies to every supplement. In the UK, supplements are not tested for safety and purity the way medicines are, so strength and quality vary between brands. If you are going to take ashwagandha, a product that has been independently tested is worth the extra cost.
Where ashwagandha fits
Here is the honest place to land. Ashwagandha is a helper, not a fix. The trials show a real, modest effect on stress and sleep for many people, and it is one of the better supported natural options in a market full of weak ones. It will not undo a schedule with no recovery in it, a bedroom full of screens, or months of overwork.
The things that move stress and sleep the most are still the unglamorous ones. Regular training, daylight in the morning, a consistent bedtime, less caffeine after lunch, and enough protein and fibre to keep energy steady. Ashwagandha can sit on top of those as a small extra, not in place of them. If your stress or sleep has been bad for a long time, that is a conversation for your doctor, not a supplement tub.
One clear next step: pick the single habit that would help your sleep or stress the most this week, and build that first. If you then want to trial a tested ashwagandha extract for eight weeks alongside it, do that with your GP's blessing if you take any medication.
Frequently asked questions
The bottom line
Ashwagandha is one of the few stress and sleep supplements with genuine trial support behind it. A 2025 meta-analysis found lower stress, lower cortisol and less anxiety, and a 2021 meta-analysis found modestly better sleep, strongest in people with insomnia who took 600 mg or more for at least eight weeks. The effects are real and worth knowing about, and they are also modest and vary between people. Respect the liver signal, avoid it in pregnancy and with existing liver disease, choose a tested product, and treat it as a small addition to the basics rather than a shortcut around them.
Sources
- Bachour and colleagues. Effects of ashwagandha supplements on cortisol, stress and anxiety levels in adults: a systematic review and meta-analysis. BJPsych Open, 2025. pmc.ncbi.nlm.nih.gov/articles/PMC12242034
- Cheah and colleagues. Effect of Ashwagandha (Withania somnifera) extract on sleep: a systematic review and meta-analysis. PLoS One, 2021. pmc.ncbi.nlm.nih.gov/articles/PMC8462692
- Vaidya and colleagues. Clinical safety and tolerability evaluation of Withania somnifera root extract in healthy human volunteers. Journal of Ayurveda and Integrative Medicine, 2023. pmc.ncbi.nlm.nih.gov/articles/PMC10784694
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Ashwagandha. National Institute of Diabetes and Digestive and Kidney Diseases. ncbi.nlm.nih.gov/books/NBK548536