Ashwagandha Lowers Cortisol, but Perceived Stress Is a Different Story
Ashwagandha (Withania somnifera) has been used in Ayurvedic medicine for thousands of years. In recent years, it has surged as “the herb that lowers cortisol” in the global supplement market. Where does the clinical evidence actually stand?
2026 Trial, 300mg Reduces Cortisol by 19%
A 60-day randomized, double-blind, placebo-controlled trial published in Medicine (2026) is worth noting. Healthy adults reporting stress received sustained-release ashwagandha root extract (AshwaSR) capsules at 150mg or 300mg doses.
Results: the 300mg group saw serum cortisol drop 19.15% from baseline, while the 150mg group showed an 11.44% reduction. Both doses improved perceived stress, sleep quality, psychological well-being, and eating behavior. No safety concerns were reported.
Across 15 Trials
A 2025 meta-analysis pooling 15 randomized controlled trials (873 participants total) found that ashwagandha supplementation reduced cortisol by an average of 2.36 mcg/dL at the 8-week mark. A separate systematic review confirmed a 1.16 mcg/dL cortisol reduction versus placebo.
The proposed mechanism involves regulation of the hypothalamic-pituitary-adrenal (HPA) axis. Under chronic stress, the HPA axis becomes overactive, keeping cortisol persistently elevated. Ashwagandha appears to dampen this overactivation.
Biomarkers and Experience Can Diverge
Here is the important gap. In some analyses, cortisol reduction reached statistical significance, but subjective perceived stress did not show a significant change. Blood test numbers can go down without a corresponding shift in how stressed someone feels.
This is less a limitation of ashwagandha than a reflection of stress itself. Cortisol is one axis of the stress response. Perceived stress is shaped by sleep, social relationships, work environment, cognitive patterns, and far more variables.
Before Starting
People with thyroid conditions or those taking thyroid medication should exercise caution, as ashwagandha can influence thyroid hormone levels. Potential interactions with immunosuppressants and sedatives also exist. If you are on prescription medication, consulting a healthcare professional comes first.