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Ashwagandha for Anxiety: What the Science Actually Shows
Ashwagandha (Withania somnifera) is now the best-selling herbal supplement globally, growing at 14% annually and reaching mainstream retail shelves from pharmacies to grocery stores. The interest is partly justified: the clinical evidence is stronger for ashwagandha than for most herbal supplements marketed for stress and anxiety. But the quality of the evidence varies considerably depending on which form and dosage you look at.
What an Adaptogen Is
Adapted from Soviet pharmacological research in the 1940s, the term adaptogen describes a substance that helps the body maintain homeostasis under stress - not by sedating the nervous system, but by modulating the physiological stress response. Ashwagandha fits this definition through its effects on the hypothalamic-pituitary-adrenal (HPA) axis, which governs cortisol production.
Unlike benzodiazepines or antihistamines, ashwagandha does not produce sedation. Its effects on stress and anxiety develop over weeks of consistent use, not hours.
What Clinical Research Shows
A 2025 systematic review analyzed 12 randomized controlled trials comparing ashwagandha to placebo for stress and anxiety. The conclusion: ashwagandha significantly reduced perceived stress and anxiety at 8 to 12 weeks compared to control groups. The effect was consistent across different formulations and dose ranges.
One widely cited 60-day randomized controlled trial used KSM-66 ashwagandha extract at 300 mg twice daily. Participants showed a 27.9% reduction in cortisol compared to placebo, along with significantly lower scores on the Perceived Stress Scale.
For sleep, one randomized controlled trial found 600 mg per day reduced sleep onset latency (time to fall asleep) by approximately 35 minutes compared to placebo. The effect is thought to be mediated through cortisol normalization rather than direct sedation.
Which Forms Have the Strongest Evidence
Not all ashwagandha products are equivalent. The active compounds are withanolides, and their concentration varies widely between products.
Generic root powder uses the whole dried root with no standardization. Withanolide content can vary dramatically between batches and manufacturers. Generic root powder is cheaper but the clinical evidence does not transfer well to unstandardized products.
KSM-66 is a full-spectrum root extract standardized to at least 5% withanolides. It has the most clinical research behind it, including the cortisol study above, and uses only the root rather than the leaves.
Sensoril uses both root and leaf material and is standardized to a higher withanolide concentration. It has good clinical evidence, though somewhat less than KSM-66.
For anxiety and cortisol reduction specifically, look for products containing KSM-66 extract at 300 to 600 mg per day. KSM-66 Ashwagandha in standardized form is what most clinical trials have used.
Dosing From Studies
Effective doses in clinical research: 300 mg KSM-66 twice daily (600 mg total) is the most commonly used protocol for stress and cortisol studies. Some studies used 300 mg once daily with significant effects, though effect sizes were smaller.
Lower doses of unstandardized root powder (500 to 1000 mg) appear in older studies and show weaker effects - likely due to variable withanolide content rather than dose-response differences.
Timing: most studies used consistent daily dosing without specifying morning or evening. For the sleep-related effects, some protocols placed the dose in the evening.
Who Should Not Take Ashwagandha
Ashwagandha is contraindicated in pregnancy - animal studies suggest it may stimulate uterine contractions. It should be avoided by anyone with autoimmune conditions (rheumatoid arthritis, lupus, multiple sclerosis) as it may stimulate immune activity.
People taking thyroid medications should consult a physician before use - ashwagandha has demonstrated thyroid-stimulating effects in some studies, which can alter thyroid hormone levels and affect medication requirements.
Side effects are generally mild at research doses: gastrointestinal discomfort (taking with food reduces this), drowsiness in some individuals, and very rarely, elevated liver enzymes with long-term high-dose use.
How It Compares to Other Evidence-Supported Approaches
For mild-to-moderate anxiety, the evidence hierarchy looks roughly like this: cognitive behavioral therapy and exercise have the strongest and most consistent evidence. Meditation, yoga, and mindfulness have substantial evidence. Magnesium (for deficient individuals) and ashwagandha have moderate evidence as supplements. The approaches are not mutually exclusive - ashwagandha makes most sense as part of a broader strategy rather than a standalone intervention.
For clinical anxiety disorders, ashwagandha does not replace pharmacological or psychological treatment. The clinical trials that show significant effects are mostly in healthy adults with elevated perceived stress, not in people with diagnosed anxiety disorders.
This content is for educational purposes only and not medical advice. Consult healthcare professionals before starting new health or fitness programs.
TopicNest
Contributing writer at TopicNest covering health and related topics. Passionate about making complex subjects accessible to everyone.
