Evidence explainerAshwagandha
Ashwagandha for Stress and Sleep: What the Trials Found, and Why the Results Vary So Much
Ashwagandha is the internet’s favorite calm-down herb. The trials do point the right way for stress and sleep, but they are small, short and wildly inconsistent. Here is what that means for you.
Key takeaways
- A 2022 meta-analysis of 12 trials (1,002 adults) found lower stress and anxiety scores than placebo, but certainty was low and results varied enormously between trials (I² of 83% and higher) [1].
- For sleep, a 2021 meta-analysis of 5 trials (400 adults) found a small improvement, larger in people with insomnia, at 600 mg/day or more and after 8 weeks or longer [2].
- Extracts differ: root (e.g. KSM-66) and root-and-leaf (e.g. Shoden, Sensoril) products are made differently, so one trial does not automatically apply to another [3].
- Trials ran about 6 to 13 weeks; longer-term safety is unknown [3].
The evidence, graded
Pulled from our monograph evidence tables. Grades follow our evidence-grading policy.
- Grade BImprovedPerceived stressStress (SMD -1.75) and anxiety (SMD -1.55) fell versus placebo. Heterogeneity was very high (I² 83–94%) and certainty of evidence was low.
- Grade BImprovedOverall sleepSmall but significant improvement in overall sleep (SMD -0.59), larger in people with insomnia. Mental alertness on rising and anxiety also improved; quality of life did not. No serious side effects reported.
- Grade CImprovedAnxiety scores (HAM-A)Hamilton Anxiety scores fell by 5.96 points versus placebo; sleep onset, total sleep time, sleep quality and efficiency also improved. Heterogeneity was extreme (I² 98%).
- Grade CImprovedMorning cortisolGreater reductions in morning cortisol and DHEA-S than placebo; Hamilton Anxiety score fell significantly, DASS-21 near-significantly. No adverse events.
Stress: a consistent direction, a shaky size
The 2022 meta-analysis pooled 12 randomized trials with 1,002 adults aged 25 to 48 [1]. Stress and anxiety scores fell versus placebo, and a dose-response analysis favored 300 to 600 mg/day for stress [1]. But heterogeneity was very high and the authors rated certainty low [1]. NIH notes that the trials in an earlier 2021 review were all from India [3].
Some trials also measured cortisol. In a 60-day trial of 60 stressed but healthy adults, a root-and-leaf extract at 240 mg/day lowered morning cortisol more than placebo [4]. Lower cortisol is a lab change, not proof you will feel calmer, but it fits the direction of the questionnaire results.
Sleep: small help, more for poor sleepers
The 2021 sleep meta-analysis pooled 5 trials with 400 adults, some healthy and some with insomnia [2]. Overall sleep improved modestly (SMD -0.59), with larger effects in people with insomnia, at doses of 600 mg/day or more, and with 8 weeks or more of use [2]. Mental alertness on waking and anxiety also improved, and no serious side effects were reported [2].
A 2024 meta-analysis of 5 trials in people with anxiety or insomnia found Hamilton Anxiety scores 5.96 points lower than placebo, with better sleep onset and quality, though heterogeneity was extreme (I² 98%) [5].
Why "ashwagandha" on a label is not one thing
Branded extracts differ in plant part and withanolide content. KSM-66 is a root extract; Shoden and Sensoril use root and leaf [3]. Studied amounts ranged from 120 to 1,250 mg/day of extract, and trials of one extract do not automatically apply to another [3]. If a product does not name its extract or standardization, it is hard to match it to any trial.
Before you try it
Common side effects across trials were mild: stomach upset, loose stools, nausea and drowsiness [3]. NIH lists possible interactions with thyroid hormone, antidiabetes, blood pressure, immunosuppressant and sedative medicines [3]. Rare liver injury and thyroid changes have been reported; we cover them in ashwagandha side effects.
If stress or sleep is the issue, the free basics still come first. Our sleep stack guide covers them, and magnesium is a popular alternative; compare magnesium glycinate vs citrate.
Quick answers
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References
- [1]Does Ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? A systematic review and meta-analysis of randomized controlled trials. Phytother Res, 2022.
- [2]Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. PLoS One, 2021.
- [3]Ashwagandha: Is it helpful for stress, anxiety, or sleep? Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2025.
- [4]An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: A randomized, double-blind, placebo-controlled study. Medicine (Baltimore), 2019.
- [5]Safety and efficacy of Withania somnifera for anxiety and insomnia: Systematic review and meta-analysis. Hum Psychopharmacol, 2024.