• Vitamins & Supplements
  • Updated August 17, 2016

Ashwagandha is a common name for the plant Withania somnifera, which is also known as "winter cherry" and "Indian ginseng." It is used in Indian traditional medicine to treat anxiety, chronic inflammation, depression, fatigue, stress, and weakness. While it is also used to improve cognition, the evidence in humans is very limited and it is unknown if ashwagandha can slow cognitive decline or prevent Alzheimer's disease. Ashwagandha is likely safe for most people though it has some drug interactions and should not be used during pregnancy.


A few studies have examined short-term cognitive effects of ashwagandha, but no studies have tested whether it can prevent age-related cognitive decline or dementia. Our search identified:

• 0 clinical studies in humans examining the treatment or prevention of cognitive decline or dementia
• 1 randomized controlled clinical trial in healthy adults examining the effects on cognitive function
• 1 randomized controlled clinical trial in bipolar disorder patients
• Numerous preclinical studies on possible mechanisms of action

Potential Benefit

It is currently unknown whether ashwagandha can prevent cognitive decline or dementia in humans. In a small double-blind placebo-controlled clinical trial, supplementation at 250 mg twice daily for 2 weeks improved psychomotor performance (reaction time) in healthy men [2]. In another randomized controlled study, patients with bipolar disorder treated with 500 mg/day experienced greater improvements in a type of working memory, a measure of reaction time, and a measure of social cognition, compared to those receiving placebo [3]. However, no benefits with ashwagandha were seen in other cognitive measures including executive function, processing speed, and psychomotor speed. Both of these trials were too small and short to determine whether ashwagandha has long-term benefits for cognitive health. Laboratory studies have shown that ashwagandha may benefit cognitive function by promoting neuronal growth and protecting neurons from damage and oxidative stress [4-7], but these benefits have not been confirmed in humans.

For Dementia Patients

It is currently unknown whether ashwagandha can improve cognition or slow cognitive decline in people with dementia. While some benefits have been observed in preclinical studies of Alzheimer's disease [6][8], ashwagandha has not been clinically studied in people with dementia.


Ashwagandha has a long history of use in traditional Indian Ayurvedic medicine, and it is generally considered safe when used properly in healthy people. However, ashwagandha can decrease blood sugar levels, lower blood pressure, and increase thyroid hormone levels, and therefore people who have those conditions or people taking medications for diabetes, high blood pressure, or thyroid conditions should exercise caution [9][10]. Ashwagandha should not be used during pregnancy as it may cause miscarriages. More information on safety and drug interactions with ashwagandha can be found on MedlinePlus.

Long-term safety has not been studied in clinical research but small clinical trials lasting 30–60 days with daily doses ranging from 300–1250 mg have reported that ashwagandha is well-tolerated with few side effects [9][11][12].

NOTE: This is not a comprehensive safety evaluation or complete list of potentially harmful drug interactions. It is important to discuss safety issues with your physician before taking any new supplement or medication.

How to Use

Ashwagandha is taken orally, either in pill form or powdered and mixed with liquids such as tea. Typical doses range from 250–2000 mg/day. Supplements commonly contain the root of the plant described either as "whole" or "extract." The extracts obtained using water versus alcohol can contain different chemicals [13]. However, which specific chemicals are bioactive is still controversial [14] and the available scientific evidence is inadequate to predict whether the effects would be better in whole versus extracted ashwagandha root or water versus alcohol extracts. Some supplements sell preparations of the plant's leaves but, according to the Ayurvedic pharmacopoeia of India, ashwagandha should be prepared from the roots [15]. As with most supplements, the content can vary depending on the bottle and brand, for example with the risk of toxins added during processing or contaminants such as heavy metals [16] if the plant was grown in a polluted area.

Learn More

Additional information and other purported uses of ashwagandha can be found at the Memorial Sloan Kettering Cancer Center.

Quality Control of Sources: United States Pharmacopeial Convention (USP) and ConsumerLab offer information on the quality of specific supplements and can assist in finding a trusted brand.

More information on safety and drug interactions with ashwagandha at MedlinePlus


  1. Pratte MA, Nanavati KB, Young V et al. (2014) An alternative treatment for anxiety: a systematic review of human trial results reported for the Ayurvedic herb ashwagandha (Withania somnifera). J Altern Complement Med 20, 901-908.
  2. Pingali U, Pilli R, Fatima N (2014) Effect of standardized aqueous extract of Withania somnifera on tests of cognitive and psychomotor performance in healthy human participants. Pharmacognosy Res 6, 12-18.
  3. Chengappa KN, Bowie CR, Schlicht PJ et al. (2013) Randomized placebo-controlled adjunctive study of an extract of withania somnifera for cognitive dysfunction in bipolar disorder. J Clin Psychiatry 74, 1076-1083.
  4. Ahmed ME, Javed H, Khan MM et al. (2013) Attenuation of oxidative damage-associated cognitive decline by Withania somnifera in rat model of streptozotocin-induced cognitive impairment. Protoplasma 250, 1067-1078.
  5. Kuboyama T, Tohda C, Komatsu K (2005) Neuritic regeneration and synaptic reconstruction induced by withanolide A. Br J Pharmacol 144, 961-971.
  6. Kuboyama T, Tohda C, Komatsu K (2006) Withanoside IV and its active metabolite, sominone, attenuate Abeta(25-35)-induced neurodegeneration. Eur J Neurosci 23, 1417-1426.
  7. Dar NJ, Hamid A, Ahmad M (2015) Pharmacologic overview of Withania somnifera, the Indian Ginseng. Cell Mol Life Sci 72, 4445-4460.
  8. Sehgal N, Gupta A, Valli RK et al. (2012) Withania somnifera reverses Alzheimer's disease pathology by enhancing low-density lipoprotein receptor-related protein in liver. Proc Natl Acad Sci U S A 109, 3510-3515.
  9. Chandrasekhar K, Kapoor J, Anishetty S (2012) 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 J Psychol Med 34, 255-262.
  10. Gannon JM, Forrest PE, Roy Chengappa KN (2014) Subtle changes in thyroid indices during a placebo-controlled study of an extract of Withania somnifera in persons with bipolar disorder. J Ayurveda Integr Med 5, 241-245.
  11. Raut AA, Rege NN, Tadvi FM et al. (2012) Exploratory study to evaluate tolerability, safety, and activity of Ashwagandha (Withania somnifera) in healthy volunteers. J Ayurveda Integr Med 3, 111-114.
  12. Andrade C, Aswath A, Chaturvedi SK et al. (2000) A double-blind, placebo-controlled evaluation of the anxiolytic efficacy ff an ethanolic extract of withania somnifera. Indian J Psychiatry 42, 295-301.
  13. Dhanani T, Shah S, Gajbhiye NA et al. (2013) Effect of extraction methods on yield, phytochemical constituents and antioxidant activity of Withania somnifera. Arabian Journal of Chemistry.
  14. Commentary – Second Supplement to the USP 33-NF 28 Reissue (PDF) US Pharmacopeial Convention.
  15. The Ayurvedic Pharmacopoeia Of India (PDF). Government of India Ministry of Health and Family Welfare Department of Ayush.
  16. Kulhari A, Sheorayan A, Bajar S et al. (2013) Investigation of heavy metals in frequently utilized medicinal plants collected from environmentally diverse locations of north western India. Springerplus 2, 676.