Does ashwagandha really lower cortisol and stress?

Ashwagandha root extract probably lowers cortisol and perceived stress in adults, based on three placebo-controlled trials of about two months.

Ashwagandha (Withania somnifera) is an herb used in traditional Ayurvedic medicine for thousands of years. It belongs to a class of herbs called adaptogens, which help the body manage stress. Modern research suggests it can lower cortisol levels and reduce feelings of anxiety and stress¹.

The root extract is the most commonly studied part of the plant. It is generally considered safe for most adults when taken in recommended doses for up to a few months.

What you can do

Trials used 240–600 mg a day of standardized root extract for about 8 weeks^2,3,4.
Pick a product that states its extract type and withanolide content, as the trials used standardized extracts².
Keep to 250–600 mg a day and up to about 12 weeks, the range reviews report as well tolerated¹.

Be careful if

May affect thyroid hormone levels: use cautiously with thyroid disorders or thyroid medication, and check with your doctor first.
The most common side effects are mild gastrointestinal symptoms¹.
Safety evidence covers use for up to about 12 weeks; long-term use is less studied¹.

Go deeper

How it works What it does in your body, in plain words 1 min

Ashwagandha's classification as an adaptogen means it helps normalize the body's physiological response to stressors rather than pushing it in one direction¹. The plant contains a group of bioactive compounds called withanolides -- steroidal lactones that are believed to drive most of its pharmacological effects.

The primary mechanism involves the hypothalamic-pituitary-adrenal (HPA) axis, the body's central stress response system. In a randomized, double-blind trial, participants taking 240 mg of ashwagandha extract daily for 60 days showed significant reductions in morning cortisol compared to placebo². Cortisol, the body's primary stress hormone, is normally elevated during chronic stress and contributes to downstream metabolic and immune disruption.

Ashwagandha also appears to modulate GABAergic signaling, which may partially explain its anxiolytic (anti-anxiety) effects³. This dual action on the hormonal stress axis and neurotransmitter systems distinguishes it from single-mechanism anxiolytics.

The evidence The studies, what they found, and how much to trust them 2 min · 4 sources

HPA Axis Modulation and Cortisol Reduction

The most robust evidence for ashwagandha centers on its effects on cortisol and perceived stress. Chandrasekhar et al. (2012) conducted a 60-day RCT with 64 subjects using 300 mg twice daily of a high-concentration full-spectrum root extract. The treatment group showed a 27.9% reduction in serum cortisol levels (p < 0.0006) and significant reductions on the Perceived Stress Scale compared to placebo³.

Lopresti et al. (2019) corroborated these findings using 240 mg/day of a standardized extract (Shoden, 35% withanolide glycosides). Salivary cortisol decreased significantly in the ashwagandha group versus placebo, alongside improvements on the Hamilton Anxiety Rating Scale (HAM-A) and the Depression, Anxiety and Stress Scale (DASS-21)².

Adaptogenic Mechanism

The adaptogenic model proposes that ashwagandha modulates the stress response at multiple points¹:

HPA axis: Reduces excessive cortisol output under chronic stress without suppressing acute cortisol responses needed for normal function.
GABAergic system: Withanolides demonstrate GABA-mimetic activity, contributing to anxiolysis and improved sleep onset.
Oxidative stress: Withaferin A and other withanolides exhibit antioxidant activity, reducing stress-induced reactive oxygen species in neural tissue.

Salve et al. (2019) demonstrated dose-dependent effects in a study comparing 250 mg/day and 600 mg/day of ashwagandha root extract over 8 weeks. Both doses significantly reduced PSS scores, but the 600 mg dose produced greater reductions in serum cortisol (p < 0.001)⁴. Sleep quality, measured by the Pittsburgh Sleep Quality Index, also improved significantly at both doses.

Safety Profile

Systematic reviews report that ashwagandha is generally well-tolerated at doses of 250-600 mg/day for up to 12 weeks¹. The most commonly reported adverse effects are mild gastrointestinal symptoms. However, ashwagandha may affect thyroid hormone levels and should be used cautiously in individuals with thyroid disorders or those taking thyroid medications.

Sources

An Overview on Ashwagandha: A Rasayana (Rejuvenator) of Ayurveda. Singh N, Bhalla M, de Jager P, Gilca M. African Journal of Traditional, Complementary and Alternative Medicines, 2011. PubMed 22754076
An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: A randomized, double-blind, placebo-controlled study. Lopresti AL, Smith SJ, Malvi H, Kodgule R. Medicine, 2019. PubMed 31517876
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. Chandrasekhar K, Kapoor J, Anishetty S. Indian Journal of Psychological Medicine, 2012. PubMed 23439798
Adaptogenic and Anxiolytic Effects of Ashwagandha Root Extract in Healthy Adults: A Double-blind, Randomized, Placebo-controlled Clinical Study. Salve J, Pate S, Debnath K, Langade D. Cureus, 2019. PubMed 32021735