Ashwagandha does appear to lower cortisol levels, and the evidence is more consistent than for most herbal supplements. Across clinical trials, standardized ashwagandha extracts taken daily reduce serum cortisol by roughly 11% to 32%, depending on the dose and duration. A 2025 systematic review and meta-analysis published in BJPsych Open confirmed statistically significant reductions in both cortisol levels and perceived stress scores after eight weeks of supplementation.
How Ashwagandha Lowers Cortisol
Cortisol is produced through a chain reaction that starts in your brain. When you perceive stress, your hypothalamus sends a chemical signal to your pituitary gland, which then tells your adrenal glands to release cortisol. This communication loop is called the HPA axis, and it’s essentially your body’s stress thermostat.
Ashwagandha appears to turn down this thermostat at multiple points. It reduces the initial stress signal from the hypothalamus and lowers the follow-up signal from the pituitary, which means your adrenal glands simply get less instruction to produce cortisol. The net effect is a quieter stress response, not a silenced one. Your body still reacts to genuine threats, but the baseline hum of cortisol output drops. This is what classifies ashwagandha as an “adaptogen,” a substance that helps normalize your stress response rather than suppressing it entirely.
What the Clinical Trials Show
One well-designed placebo-controlled trial tested 240 mg daily of a concentrated ashwagandha extract in healthy but stressed adults. After the study period, the ashwagandha group showed a 23% reduction in morning cortisol levels. The placebo group had virtually no change (a 0.5% increase). The effect was consistent across genders: women saw a 25% cortisol reduction and men saw 22%.
These aren’t isolated findings. A 2021 systematic review of seven randomized trials, covering 491 adults, found that ashwagandha consistently reduced serum cortisol compared to placebo across studies lasting six to eight weeks. A separate meta-analysis confirmed significant reductions in cortisol, perceived stress scores, and anxiety scores, all from the same intervention.
The cortisol reduction also tracks with how people actually feel. In the meta-analysis, participants taking ashwagandha reported meaningfully lower scores on the Perceived Stress Scale alongside their lower cortisol numbers. This matters because it suggests the hormonal change translates into a real, noticeable difference in daily stress levels, not just a lab value shift.
Dosage and Timeline
Most positive trials use standardized extracts in the range of 240 to 600 mg per day. The word “standardized” is key here, because raw ashwagandha powder and concentrated extracts are not interchangeable. Extracts are processed to contain a specific percentage of active compounds called withanolides, so 240 mg of a concentrated extract can be more potent than 1,000 mg of plain root powder. When shopping for a supplement, look for a named extract (KSM-66 and Shoden are two of the most studied) and check the withanolide percentage on the label.
Lower doses can still work. One trial found that just 225 mg per day of a root and leaf extract produced lower salivary cortisol levels than placebo after 30 days. Higher doses up to 600 mg daily have also shown benefits without a clear pattern of “more is better” within that range.
As for timing, don’t expect overnight results. Most studies measure outcomes at the 6 to 8 week mark, and that’s the window where cortisol reductions become statistically clear. Some trials have seen early signals at 30 days, while at least one study extended supplementation to 90 days with sustained benefits. If you’ve been taking ashwagandha for two weeks and feel nothing, that’s normal. Give it at least a month before judging whether it’s working for you.
Ashwagandha for Exercise-Related Stress
Cortisol doesn’t just rise from work deadlines and poor sleep. Intense exercise is a significant cortisol trigger, and chronically elevated training stress, especially when paired with inadequate recovery or poor nutrition, can keep cortisol persistently high. This is the hormonal signature of overtraining.
A systematic review of ashwagandha’s effects in athletes and active adults found that the same HPA axis modulation that helps with psychological stress also applies to exercise-induced cortisol spikes. By blunting excessive cortisol output after training, ashwagandha may support recovery and reduce the physiological toll of high training volumes. The evidence here is still thinner than for general stress, but the biological mechanism is the same, and several studies in active populations report improved recovery markers alongside lower cortisol.
Who Should Avoid It
Ashwagandha is generally well tolerated in the doses used in clinical trials (up to 600 mg daily for up to 12 weeks), but it isn’t safe for everyone. The National Institutes of Health specifically flags three groups who should not take it:
- People with thyroid disorders. Ashwagandha can increase thyroid hormone levels, which is dangerous if you have hyperthyroidism or Hashimoto’s thyroiditis.
- People with autoimmune conditions. Because ashwagandha stimulates immune activity, it can worsen conditions where the immune system is already overactive.
- People with hormone-sensitive prostate cancer. Ashwagandha can raise testosterone levels, which may fuel tumor growth.
If you’re scheduled for surgery, stop taking ashwagandha beforehand, as it may interact with anesthesia and other medications used during procedures. And because most clinical trials have lasted 6 to 12 weeks, there’s limited data on what happens with continuous use beyond three months. Some people cycle on and off (eight weeks on, two to four weeks off), though this is a practical convention rather than something proven necessary by research.
Realistic Expectations
A 15% to 25% cortisol reduction is meaningful, but it’s not going to overpower the effects of chronic sleep deprivation, an overwhelming workload, or untreated anxiety. Ashwagandha works best as one piece of a broader stress management approach. If your cortisol is elevated because of a lifestyle that never lets your nervous system rest, a supplement can take the edge off, but it can’t fix the root cause.
It’s also worth noting that cortisol itself isn’t the enemy. You need cortisol to wake up in the morning, respond to challenges, and regulate inflammation. The problem is chronically elevated cortisol, the kind that comes from weeks or months of unrelenting stress. That’s the pattern ashwagandha appears to correct: not eliminating cortisol, but pulling it back toward a healthier baseline.