Ashwagandha
Withania somnifera
The classic adaptogen for stress and cortisol regulation.
Evidence tier
Moderate
Research weight
Citations
18 verified / 18
Classification
Ayurvedic
❝
What the evidence says. Graded moderate: multiple short RCTs show real reductions in stress, cortisol and anxiety, but most run ≤12 weeks and are industry-funded, and a 2025 meta-analysis found no change in perceived stress — so the benefit is likely real but modest and not yet proven durable. (Moderate evidence: Several controlled trials; effects real but modest or context-dependent.)
What is Ashwagandha?
Ashwagandha (Withania somnifera) is an Ayurvedic herb used for stress & anxiety relief. NutriDex grades the human evidence as Moderate. Ashwagandha is the most-studied Ayurvedic adaptogen. Randomized controlled trials report meaningful reductions in perceived stress and serum cortisol (often 20–30%) over 6–8 weeks, alongside modest improvements in sleep quality and anxiety scores. Smaller trials suggest gains in muscle strength, recovery, and testosterone in men. Most trials are short (≤12 weeks) and industry-funded, so long-term safety and effect durability remain less certain.
Purported Benefits
✓Stress & anxiety relief
✓Lower cortisol
✓Improved sleep
✓Strength & recovery
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
| Outcome | Evidence | Effect | Studies |
|---|---|---|---|
| Stress & perceived-stress reductionMultiple RCT meta-analyses show reduced PSS scores, but newest pooled analyses are inconsistent and trials are short and industry-funded. | Moderate | ↑ benefit · moderate | 4 |
| Cortisol loweringRCTs and meta-analyses consistently show ~20-30% serum cortisol reduction, though one 2025 RCT found no cortisol change. | Moderate | ↑ benefit · moderate | 4 |
| Anxiety reductionPooled RCTs show HAM-A reductions, but heterogeneity is high and samples small. | Moderate | ↑ benefit · moderate | 3 |
| Sleep qualityMeta-analysis of 5 RCTs found small-but-significant sleep improvement (SMD -0.59), larger in insomnia and >=600mg. | Moderate | ↑ benefit · small | 3 |
| Strength & physical performanceBayesian meta-analysis of ~13 small trials shows modest strength/VO2max gains; risk of bias and small samples limit confidence. | Preliminary | ↑ benefit · small | 2 |
| Male testosterone & reproductive functionSingle RCT (~17% testosterone rise) plus reviews of infertile men; mostly baseline-controlled, few RCTs, authors call it preliminary. | Preliminary | ↑ benefit · moderate | 2 |
| Liver injury (safety)Case series of 23 ashwagandha-associated liver-injury cases (3 deaths); rare signal, while a 12-month study found no hepatic changes. | Preliminary | ⚠ risk | 1 |
Dosing & Compounds
Typical Dose
300–600 mg/day of root extract (standardized to 5% withanolides), often split AM/PM.
Active Compounds
Safety & Cautions
Avoid in pregnancy (traditionally abortifacient) and while breastfeeding. Commonly causes GI upset and drowsiness, and may aggravate autoimmune thyroid disease or interact with sedatives, thyroid medication and immunosuppressants. Uncommon but serious liver injury has been reported — including a case series with deaths in people with pre-existing liver disease — so stop and seek care for jaundice, dark urine, or right-upper-abdominal pain. Educational only — always check with your doctor or pharmacist before combining Ashwagandha with any medicine.
Ashwagandha drug interactions
Known or theoretical interactions between Ashwagandha and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining Ashwagandha with any medicine.
Monitor
Benzodiazepines, sedatives, alcohol
May add to drowsiness and sedation when combined with CNS depressants.
Ashwagandha can have mild sedative/anxiolytic effects that may add to CNS-depressant drugs. NIH ODS — Ashwagandha
Key Studies ★ 18 studies
Meta-analysis
Della Porta 2024 meta-analysis
✓ PubMed
Across 5 RCTs (n=254), Withania somnifera significantly reduced anxiety (HAM-A MD -5.96, 95% CI -10.34 to -1.59) and improved sleep onset latency and quality, though heterogeneity was high.
Meta-analysis
Bachour 2025 meta-analysis (BJPsych Open)
✓ PubMed
Pooled RCTs of adults found ashwagandha significantly lowered serum cortisol but showed no significant change in perceived stress, with no improvement in quality of life.
Meta-analysis
BJPsych Open 2025 meta-analysis (mental disorders)
✓ PubMed
Systematic review and meta-analysis found ashwagandha reduced symptoms in people with diagnosed mental disorders, with greater benefit at lower doses (<=500 mg/day) and longer interventions (>8 weeks).
systematic review
Roy 2025 systematic review (Phytotherapy Research)
✓ PubMed
PRISMA systematic review of sex-specific reproductive outcomes concluded Withania somnifera improves male sperm count and quality (via hormone regulation and antioxidant effects) and may benefit female reproductive disorders such as PCOS and stress-related menstrual irregularities, though evidence remains preliminary.
Meta-analysis
Della Porta 2025 (BJPsych Open)
✓ Full text
Meta-analysis of 15 RCTs (n=873) found ashwagandha reduced perceived stress (PSS mean change -4.88; 95% CI -7.84 to -1.91), anxiety (HAM-A -3.52; 95% CI -6.00 to -1.04), and cortisol (-2.36; 95% CI -3.26 to -1.46) versus placebo at 8 weeks.
Meta-analysis
Bonilla 2021 meta-analysis
✓ Full text
Small-to-moderate gains in strength and VO₂max across 12 RCTs.
Systematic review
Cheah 2021 meta-analysis
✓ Full text
Pooled 5 RCTs (n=400) found ashwagandha extract produced a small-to-moderate improvement in overall sleep (SMD -0.59, 95% CI -0.75 to -0.42).
Meta-analysis
Cheah et al. 2021 (PLoS One)
✓ PubMed
Meta-analysis of 5 RCTs (400 adults): Ashwagandha extract produced a small but significant improvement in overall sleep (SMD -0.59, 95% CI -0.75 to -0.42; I2=62%), with larger effects in those with insomnia, doses >=600 mg/day, and duration >=8 weeks. Also improved morning mental alertness and anxiety; no serious adverse effects.
Meta-analysis
Bonilla et al. 2021 (J Funct Morphol Kinesiol)
✓ PubMed
PRISMA systematic review and Bayesian meta-analysis of 13 trials (12 quantitative) in healthy adults: Ashwagandha supplementation was more efficacious than placebo for physical-performance outcomes, including strength/power, cardiorespiratory fitness (VO2max), and fatigue/recovery; low-to-moderate overall risk of bias.
Systematic review
Durg et al. 2018 (Phytomedicine)
✓ PubMed
Evidence-based systematic review/meta-analysis in infertile men (4 trials/5 publications). W. somnifera increased sperm concentration (+167%), semen volume (+59%), sperm motility (+57%), serum testosterone (+17%) and LH (+34%) vs baseline after 90 days; pooled observational data confirmed improved semen parameters (e.g., sperm concentration MD +13.57 million/ml, 95% CI 11.12-16.01). Evidence limited by only 1 RCT; no adverse effects reported.
RCT
Kale 2024 (RCT)
✓ PubMed
In adults (n=120) given 600 mg/day for 8 weeks, ashwagandha root extract improved episodic memory, working memory, attention accuracy, mood and executive function vs placebo, well tolerated.
RCT
Ballesteros-Torres 2025 (RCT, Nutrition & Metabolism)
✓ Full text
Double-blind placebo-controlled pilot RCT in adults with overweight/obesity (n=43, 500 mg/day x 40 days) found ashwagandha significantly reduced triglycerides (-31.3 mg/dL, p=0.008) and VLDL-cholesterol (p=0.03) but produced no significant change in body weight, BMI, or waist circumference.
RCT
Zenroot RCT 2025 (Advances in Therapy)
✓ PubMed
84-day double-blind placebo-controlled RCT (n=90) of 125 mg ashwagandha extract (1.5% withanolides) showed significant improvements in Perceived Stress Scale, Beck Anxiety Inventory, and PSQI sleep scores at days 28/56/84, with no significant change in serum cortisol.
RCT
Chauhan 2022 (RCT)
✓ Source
In a 8-week double-blind RCT of adult men, ashwagandha root extract raised serum testosterone ~17% (vs 2% placebo) and improved DISF-M sexual function and well-being scores.
Safety / toxicology
Philips 2023 (case series)
✓ PubMed
Case series from India of 23 patients with ashwagandha-associated liver injury (8 single-ingredient), predominantly cholestatic; 3 with chronic liver disease developed acute-on-chronic failure and died.
RCT
Chandrasekhar 2012
✓ PubMed
300mg KSM-66 cut perceived-stress scores ~44% and serum cortisol ~28% vs placebo (n=64).
observational study
Verma 2025 12-month safety study (Phytotherapy Research)
✓ PubMed
Prospective multi-centre observational study of healthy adults (N=191, 18-65 y) taking standardized ashwagandha root extract for 12 months reported no serious adverse events and no clinically significant changes in hepatic, renal, thyroid, or hematological parameters.
Study
Salve 2019
✓ PubMed
Improved sleep onset and quality at 600mg/day over 8 weeks.