Quick Facts
- TypeAdaptogenic herb
- Also Known AsWithania somnifera, Indian ginseng, winter cherry
- Active CompoundsWithanolides (steroidal lactones)
- Common Dosage300–600 mg/day (root extract)
- Strongest Evidence ForAnxiety (4+ meta-analyses)
- Time to Effect6–8 weeks (median)
What Is Ashwagandha
Ashwagandha is a shrub native to India, the Middle East, and parts of Africa. It has been used in Ayurvedic medicine for over 3,000 years and is classified as an "adaptogen" — a substance theorized to help the body resist physiological and psychological stress. The active compounds, withanolides, are steroidal lactones concentrated primarily in the root.
In modern clinical research, ashwagandha has become one of the most studied herbal supplements, with particular strength in the anxiety and stress domains. Unlike many traditional remedies, it has been evaluated in multiple independent meta-analyses with consistent positive findings.
Extract Types
| Extract | Plant Part | Standardization | Typical Dose |
|---|---|---|---|
| KSM-66 | Root only | 5% withanolides | 600 mg/day |
| Sensoril | Root + leaf | 10% withanolide glycosides | 125–250 mg/day |
| Shoden | Root + leaf | 35% withanolide glycosides | 120 mg/day |
KSM-66 is the most frequently studied extract. Higher withanolide concentrations (Sensoril, Shoden) allow lower effective doses. Direct dose comparisons between extracts are unreliable due to differing standardization methods.
What the Evidence Shows
| Condition | Evidence | Key Finding |
|---|---|---|
| Anxiety | Strong | 4+ meta-analyses: SMD -1.55 to -6.87; dose-response confirmed[1][2] |
| Stress / cortisol | Strong | Significant cortisol reduction (MD = -2.58) and stress score reduction[3] |
| Sleep | Moderate | SMD -0.59 for overall sleep quality; greater benefit at ≥600mg/day, ≥8 weeks[4] |
| Depression | Moderate | Significant reduction (SMD = -5.68) in dose-response meta-analysis[1] |
| Testosterone / male fertility | Moderate | Multiple studies report increased testosterone and improved semen parameters; more large RCTs needed |
| Exercise performance | Limited | Some evidence for improved VO2 max and strength in trained individuals; inconsistent results |
| Cognitive function | Limited | Small studies suggest improved reaction time and attention; insufficient for conclusions |
| Blood sugar | Limited | Preliminary evidence for reduced fasting glucose; very few studies |
Deep Dives by Condition
Safety & Drug Interactions
The Marchi et al. 2025 meta-analysis of 14 studies found no significant safety or tolerability differences between ashwagandha and placebo.[6] Side effects, when reported, were mild: GI discomfort and drowsiness.
Important Safety Concerns
- Thyroid effects: Ashwagandha can increase thyroid hormones (T3, T4). People with hyperthyroidism or on thyroid medication should consult their provider. Those with hypothyroidism may see a beneficial effect, but this requires monitoring.
- Liver injury: Rare cases of liver toxicity have been reported. WHO and some regulatory agencies have issued advisories. Those with liver disease should avoid use.
- Pregnancy: Not recommended. Insufficient safety data; some traditional texts classify it as an abortifacient.
- Autoimmune conditions: As an immunomodulator, ashwagandha may stimulate immune activity. Generally not recommended for lupus, rheumatoid arthritis, or multiple sclerosis.
Drug Interactions
| Drug Class | Interaction | Risk |
|---|---|---|
| Sedatives / CNS depressants | Additive sedation | Moderate |
| Thyroid medications | May alter thyroid hormone levels | Moderate |
| Immunosuppressants | May counteract immunosuppression | High |
| Blood sugar medications | May enhance hypoglycemic effect | Moderate |
| Blood pressure medications | May lower BP further | Low–Moderate |
References
- Alsanie SA, et al. "Effects of ashwagandha on mental health in adults: dose-response meta-analysis of 22 RCTs." Complement Ther Med. 2026. PubMed
- Akhgarjand C, et al. "Ashwagandha supplementation for anxiety and stress." Phytother Res. 2022. 12 RCTs, 1,002 participants. PubMed
- Arumugam V, et al. "Ashwagandha on stress and anxiety: meta-analysis." Explore (NY). 2024. 9 RCTs, 558 patients. PubMed
- Cheah KL, et al. "Effect of Ashwagandha extract on sleep." PLoS One. 2021. 5 RCTs, 400 participants. PubMed
- Fatima K, et al. "Safety and efficacy for anxiety and insomnia." Hum Psychopharmacol. 2024. 5 RCTs. PubMed
- Marchi M, et al. "Ashwagandha for mental health symptoms." BJPsych Open. 2025. 14 studies. PubMed