Ashwagandha for stress and sleep: benefits and risks

A plant is not one standard product

Ashwagandha (Withania somnifera) is used in traditional medicine and sold in products made from different plant parts and extracts. A study of one preparation does not establish the effects or quality of every capsule. Labels such as “adaptogen” do not by themselves show that a product will improve stress, sleep or health.

For context on stress, anxiety and support beyond products, see stress and mood.12

What did a short stress study find?

In a 2019 double-blind, placebo-controlled trial, stressed healthy adults received a particular ashwagandha extract or placebo for 60 days. The authors reported a statistically significant difference on one anxiety rating scale, while the difference on another stress-related scale was not statistically significant. The supplier, Arjuna Natural, funded the study and provided the extract. This short study does not establish long-term safety, effects of other products or a treatment for an anxiety disorder.

The trial enrolled 60 adults who described themselves as highly stressed; it was not a trial of people selected for a diagnosed anxiety disorder. All 60 completed the study, and the authors reported no adverse events during those 60 days. That reassuring observation is limited by the small group and short follow-up: it cannot exclude uncommon reactions, delayed effects or harms from other preparations.3

Does ashwagandha increase testosterone or improve vitality?

Some small, short studies suggest a change in testosterone, but a hormone measurement is not the same as improved fertility, strength, sexual function or treatment of low testosterone. In a 2019 double-blind crossover study, 57 men aged 40–70 with overweight and mild fatigue were enrolled; 43 completed both eight-week periods. Salivary testosterone increased 14.7% more with the tested extract than with placebo, but the study did not find statistically significant between-treatment differences in fatigue, vigour or sexual well-being. Saliva collection at home and participant dropouts add uncertainty. The extract manufacturer, Arjuna Natural, funded the trial.

In another short 2019 study of stressed adults, testosterone rose over time in men taking an extract, but the change was not statistically significant compared with placebo. NIH describes limited evidence for testosterone and sperm quality and advises people with hormone-sensitive prostate cancer to avoid ashwagandha. Neither study establishes a treatment for infertility or low testosterone; symptoms and specific products warrant discussion with a clinician.531

What is still uncertain about sleep and anxiety?

The US National Center for Complementary and Integrative Health says some preparations may help with stress and insomnia, but evidence for anxiety is unclear. Studies differ in participants and formulations. Persistent sleep or anxiety symptoms can have many causes and deserve professional assessment; do not replace prescribed care with a supplement. For a different sleep-related product, see melatonin and sleep.1

Safety and possible liver injury

Stomach upset and drowsiness can occur; long-term safety is not well established. Australia’s Therapeutic Goods Administration describes very rare reports of liver injury associated with ashwagandha products and advises people with existing liver disorders to avoid them. Reports do not establish the risk for every product or person, but a serious possible harm should not be dismissed. The Australian TGA advises stopping ashwagandha immediately and seeking medical advice if you develop yellowing of the skin or eyes, dark urine, nausea, vomiting, unusual tiredness, weakness, abdominal pain or loss of appetite. Tell the clinician about all products taken. Sudden vomiting or diarrhoea can also occur as a separate acute reaction; the TGA advises stopping use and seeing a doctor for assessment. For a different herbal product and its separate safety evidence, see turmeric and curcumin.147

Can ashwagandha affect the thyroid?

It may affect thyroid hormone levels, but that does not make it an established thyroid treatment. In an eight-week placebo-controlled pilot study, 50 adults with a mild thyroid blood-test abnormality were assigned a particular root extract or placebo; four withdrew early. The extract group had lower thyroid-stimulating hormone and higher thyroid hormones on blood tests than the placebo group. The small, short study did not establish lasting symptom improvement or long-term safety. Ixoreal Biomed supplied the extract; the authors declared no competing financial interests.

Separately, NIH describes case reports of people who developed thyrotoxicosis—symptoms and effects caused by too much thyroid hormone—while taking ashwagandha. Case reports cannot establish how often this happens or prove that every product caused the problem. A faster or irregular heartbeat, tremor or unexplained weight loss can have different causes and deserve medical assessment. NIH advises against ashwagandha for people with thyroid disorders and notes possible interactions with thyroid hormone medicines. Do not alter prescribed thyroid medicine because of a supplement; discuss the exact product and medicines with a clinician.621

Medicines, pregnancy and product questions

Ashwagandha may interact with medicines including sedatives, anti-seizure medicines, thyroid hormones, immunosuppressants and some diabetes or blood-pressure medicines. The NIH advises against its use during pregnancy or breastfeeding, in people with thyroid or autoimmune disorders, and for people about to have surgery. Discuss the exact product and medicines with a healthcare professional before starting or stopping. This guide does not recommend a dose; see supplement interactions and the label guide.1