Ashwagandha (Withania somnifera) has substantial human clinical research behind its use for stress support and sleep. Randomized controlled trials and meta-analyses have reported improvements in perceived stress, anxiety-rating scores, serum cortisol and sleep outcomes.
This guide focuses on what those human studies found, the preparations and amounts they studied, how ashwagandha fits into a stress-and-sleep routine, and the safety considerations that genuinely matter.
Key Takeaways
- Stress: a 2024 systematic review and meta-analysis of nine randomized controlled trials involving 558 participants found significant improvements in Perceived Stress Scale scores compared with placebo.
- Anxiety-rating scores: the same meta-analysis found significant improvement on the Hamilton Anxiety Scale.
- Cortisol: the 2024 meta-analysis and individual placebo-controlled trials reported significant reductions in serum or morning cortisol.
- Sleep: a systematic review and meta-analysis of five randomized controlled trials involving 400 adults found significant improvement in overall sleep, along with improvement in mental alertness on rising.
Together, these findings make ashwagandha one of the more clinically studied botanicals used in modern stress-and-sleep supplements.
What is ashwagandha?
Ashwagandha is an Ayurvedic botanical traditionally used as a rasayana and now commonly described as an adaptogen—a botanical used to support the body's response to stress. Its scientific name is Withania somnifera.
Ashwagandha contains a range of naturally occurring compounds, including withanolides. Modern supplements can use root powder, root extract, leaf extract or combinations of root and leaf, and many clinical trials use standardized extracts rather than unstandardized whole-herb powder.
That distinction matters because two products that both say “ashwagandha” on the front label can contain materially different preparations.
Ashwagandha for stress: what the strongest evidence shows
2024 meta-analysis: nine randomized trials and 558 participants
A 2024 systematic review and meta-analysis published in Explore pooled nine randomized controlled trials involving 558 participants. Compared with placebo, ashwagandha formulations produced significant improvements across three important stress-related outcomes:
- Perceived Stress Scale: mean difference -4.72 (95% CI -8.45 to -0.99);
- Hamilton Anxiety Scale: mean difference -2.19 (95% CI -3.83 to -0.55);
- serum cortisol: significant reduction versus placebo, with a pooled mean difference of -2.58 (95% CI -4.99 to -0.16).
The authors concluded that the included ashwagandha formulations had beneficial effects on stress and anxiety outcomes. Read the 2024 systematic review and meta-analysis on PubMed.
60-day trial: 600 mg per day of a root extract
In a randomized, double-blind, placebo-controlled trial, 64 adults with chronic stress received either placebo or 300 mg of a high-concentration full-spectrum ashwagandha root extract twice daily—600 mg per day—for 60 days.
At day 60, the ashwagandha group showed significant reductions across all of the study's stress-assessment scales compared with placebo (P<0.0001). Serum cortisol was also significantly reduced relative to placebo (P=0.0006). No serious adverse events were reported. Read the randomized trial in the Indian Journal of Psychological Medicine.
Another randomized trial found lower anxiety scores and morning cortisol
A 2019 randomized, double-blind, placebo-controlled study enrolled 60 healthy adults reporting high stress. Participants received placebo or 240 mg per day of a standardized ashwagandha extract for 60 days.
Compared with placebo, the ashwagandha group had a significant reduction in Hamilton Anxiety Rating Scale scores (P=.040) and a greater reduction in morning cortisol (P<.001). The study also measured DHEA-S and other hormonal outcomes as part of its investigation of the stress response. Read the randomized trial published in Medicine.
Why cortisol matters in ashwagandha research
Cortisol is a hormone involved in the body's physiological response to stress. What makes the ashwagandha literature useful is that several studies have measured more than self-reported feelings: they have also measured cortisol as an objective biomarker.
The 2012 and 2019 randomized trials both reported greater cortisol reductions with ashwagandha than with placebo, and the 2024 meta-analysis found the same direction of effect across pooled trials.
The 2019 researchers proposed that effects on the hypothalamic-pituitary-adrenal stress-response system may help explain the findings. The exact biological pathways are still being investigated, but the human cortisol data provide a measurable clinical signal alongside the questionnaire results.
Ashwagandha for sleep: evidence from randomized trials
Stress support is not the only area with human data. Ashwagandha has also been evaluated specifically for sleep.
A systematic review and meta-analysis published in PLOS ONE analyzed five randomized controlled trials with 400 adults. Ashwagandha extract significantly improved overall sleep compared with placebo, with a standardized mean difference of -0.59 (95% CI -0.75 to -0.42).
The sleep effects were more pronounced in participants with insomnia, in studies using at least 600 mg per day, and in studies lasting at least eight weeks. The analysis also found improvement in mental alertness on rising and anxiety level. No serious side effects were reported in the included trials. Read the systematic review and meta-analysis on PubMed.
These findings support ashwagandha as a research-backed option for people building a nighttime routine around stress management and sleep support. It should not be presented as a drug treatment for insomnia or an anxiety disorder.
If you are deciding between ashwagandha and magnesium for a nighttime routine, read our Ashwagandha vs Magnesium for Sleep: Differences, Evidence & Can You Take Them Together? comparison.
How long was ashwagandha used in the studies?
The clinical research points toward consistent daily use over a period of weeks, rather than treating ashwagandha like an immediate sedative.
- The 2012 stress trial used 600 mg per day for 60 days.
- The 2019 stress trial used 240 mg per day for 60 days.
- In the sleep meta-analysis, sleep effects were more pronounced in studies lasting eight weeks or longer.
These amounts should be read in the context of the specific extracts studied. Extract concentration, plant part and standardization can differ, so milligrams alone are not enough to determine whether two ashwagandha products are equivalent.
What to look for in an ashwagandha supplement
- Botanical identity. The label should clearly identify Withania somnifera.
- Plant part. Look for whether the formula uses root, leaf or a root-and-leaf extract.
- Extract versus powder. Clinical research often uses concentrated extracts, so this distinction helps you compare a label with a study.
- Standardization. If the extract is standardized to withanolides or another constituent, the label should state that information clearly.
- Amount per serving and serving size. Compare the full daily serving—not just the amount in a single capsule.
- Clear directions and warnings. A high-quality label should make both easy to find.
Ashwagandha versus Rhodiola: they are not interchangeable
Ashwagandha and Rhodiola are often grouped together under the term “adaptogens,” but they are different botanicals with different clinical research profiles. Ashwagandha has direct randomized-trial and meta-analytic evidence around perceived stress, cortisol and sleep. Rhodiola has its own body of research, often centered on fatigue, stress-related performance and endurance-related outcomes.
If your primary goal is to evaluate an ingredient for a stress-and-sleep routine, the ashwagandha evidence above is the more directly relevant evidence base to review.
Safety considerations that matter
Ashwagandha is commonly used, but there are several safety situations worth taking seriously. The U.S. National Center for Complementary and Integrative Health notes that short-term use has been studied more extensively than long-term use and lists several important precautions.
- Ashwagandha should be avoided during pregnancy and should not be used while breastfeeding.
- Rare cases of liver injury have been reported in association with ashwagandha supplements.
- It is not recommended for people who are about to have surgery or who have certain thyroid or autoimmune disorders without medical guidance.
- Potential medication interactions include medicines for diabetes or high blood pressure, immunosuppressants, sedatives, anti-seizure medicines and thyroid hormone medication.
- Some people may experience drowsiness or gastrointestinal effects.
Review the NCCIH ashwagandha safety guidance. If you take prescription medication, have a medical condition, are preparing for surgery, or are pregnant or breastfeeding, discuss ashwagandha with a qualified healthcare professional before use.
The bottom line
Human clinical research supports ashwagandha as an evidence-based botanical option for stress support, with additional evidence for sleep. A 2024 meta-analysis of nine randomized trials found improvements in perceived stress, anxiety-rating scores and cortisol. Individual placebo-controlled trials have also reported reductions in stress scores and cortisol, while a separate meta-analysis of five randomized trials found improvement in overall sleep and mental alertness on rising.
The practical takeaway is to compare the preparation used in research with the supplement label in front of you: botanical identity, plant part, extract type, standardization, amount per serving and directions all matter.
Explore an ashwagandha option
If you are comparing ashwagandha supplements, you can review the Supplement Facts, directions and warnings for Zen Mode™ here.
References
- Effects of Ashwagandha (Withania somnifera) on stress and anxiety: A systematic review and meta-analysis. Explore. 2024. PMID: 39348746.
- A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adults. Indian Journal of Psychological Medicine. 2012;34(3):255-262. DOI: 10.4103/0253-7176.106022.
- An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: A randomized, double-blind, placebo-controlled study. Medicine. 2019. PMID: 31517876.
- Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. PLOS ONE. 2021. DOI: 10.1371/journal.pone.0257843.
- Ashwagandha: Usefulness and Safety. National Center for Complementary and Integrative Health.
This article is for educational purposes and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the U.S. Food and Drug Administration. Dietary supplements are not intended to diagnose, treat, cure, or prevent any disease. Consult a qualified healthcare professional before beginning a new supplement if you take prescription medication, have a medical condition, or are pregnant or breastfeeding.