Ashwagandha lowers cortisol

A pooled analysis found ashwagandha lowered cortisol more than placebo, though the result was near the significance threshold and sensitive to single trials. A 2026 meta-analysis of 12 randomized placebo-controlled trials that measured cortisol found it fell more on ashwagandha than on placebo, but the result only just reached statistical significance (p = 0.04), the size of the effect varied enormously between trials, with one trial accounting for much of that variation, and there were signs that smaller or null results are missing from the published record.

The one trial designed around cortisol found a smaller gap. In 141 stressed adults, with the change in blood cortisol declared in advance as the main outcome, 600mg a day of ashwagandha root extract for 8 weeks lowered cortisol by 2.55 μg/dL against 1.10 on placebo, a difference that was not statistically significant. No trial has tested how the adrenal glands work after cortisol falls, and three case reports describe underactive adrenal glands in people taking ashwagandha. Beyond about three months, safety has been followed in one 12-month study with no comparison group, sponsored by the extract's maker, and rare but serious liver injury has been reported.

The trials behind the clearer results were small, and those cited here were funded or supplied by the makers of the extract being tested. In a 60-day trial of 60 stressed adults taking 240mg a day of a root-and-leaf extract, morning cortisol fell 23% while placebo was essentially unchanged; cortisol was a secondary outcome and the trial was registered after it had run. A crossover trial of 57 overweight men aged 40 to 70 taking the same extract for 8 weeks found no difference from placebo in salivary cortisol. A 2023 review of nine trials lasting 30 to 112 days found cortisol falling across them and reported that none assessed adrenal function or long-term effects. The 12-month study followed 191 adults without unstable liver, kidney or heart disease who took 600mg a day of a root extract: blood cortisol was about 9% lower at the end, liver, kidney and thyroid blood tests showed no clinically significant change, and adrenal function was not tested. With no comparison group, it cannot show what the extract itself did.

Most of this research enrolled otherwise healthy adults who reported stress, mostly in India, and tested branded extracts that differ from each other in plant part, dose and withanolide content. Cortisol was usually a single morning blood or saliva reading, although cortisol swings through the day. People with conditions that change cortisol, such as Cushing's syndrome or adrenal insufficiency, were not among those studied, and at least one trial excluded people taking steroid medicines, so the results do not describe them. The most recent of the three case reports, from 2026, describes a 55-year-old woman who had taken about 950mg of ashwagandha a day for a year, in several herbal products that also contained other herbs: her morning cortisol was barely measurable and her adrenal glands responded weakly to a stimulation test. The products were not laboratory-tested for added steroids, a recognised cause of the same picture, so the report cannot show that ashwagandha was the cause. An earlier report, from 2022, describes a 41-year-old woman who took a single branded root extract, about 860mg a day, and no steroid medicines: after about ten weeks her adrenal glands barely responded to a stimulation test, and about two weeks after she stopped, the same test was normal. Her symptoms did not change, the product was not laboratory-tested, and one case cannot show how often this happens or that ashwagandha was the cause. In rats, ashwagandha lowered the brain and pituitary signals that tell the adrenal glands to release stress hormone as well as the hormone itself, which suggests the effect starts upstream of the adrenal glands.

The NIH describes ashwagandha as well tolerated for up to about three months, usually with mild side effects such as stomach upset and drowsiness, and notes that long-term safety is unknown. The US LiverTox database rates it a likely cause of liver injury, typically appearing 2 to 12 weeks after starting, with rare deaths and emergency liver transplants mostly in people with existing liver disease. The same 2026 meta-analysis found a small rise in the thyroid hormone T4, cases of an overactive thyroid have been reported, and the NIH notes it might interact with thyroid medication as well as with diabetes, blood pressure, immune-suppressing and sedative medicines. US prescribing labels for digoxin, a heart medicine, also warn that ashwagandha can interfere with some digoxin blood tests, making the measured level read higher than it is. Some experts advise against use in pregnancy, France's food safety agency recommended in 2024 against use during pregnancy and breastfeeding and by people with endocrine disorders, and Denmark banned ashwagandha in 2023.