Several herbs have clinical evidence showing they can reduce cortisol, the hormone your body releases in response to stress. The most studied options are ashwagandha, holy basil, rhodiola rosea, and bacopa monnieri. Most take anywhere from one to eight weeks of consistent use before measurable changes in cortisol show up, and the strength of evidence varies considerably from herb to herb.
Ashwagandha
Ashwagandha is the most widely researched cortisol-lowering herb. Multiple randomized, placebo-controlled trials have found it significantly reduces serum cortisol compared to placebo, alongside improvements in self-reported stress, sleep quality, and fatigue. Doses in clinical trials range from 240 to 1,250 mg per day of root extract, with many studies using around 300 to 600 mg daily. One 90-day trial gave participants a single 300 mg capsule per day and found lower serum cortisol and better stress scores compared to placebo.
Studies generally demonstrate the herb’s safety for up to 8 weeks at doses up to 600 mg per day. If you’re on thyroid medication, use caution, as ashwagandha can stimulate thyroid hormone activity. It should also be avoided during pregnancy and used carefully alongside sedating medications.
Holy Basil (Tulsi)
Holy basil has some of the most detailed cortisol data of any adaptogenic herb. In a double-blind trial published in Frontiers in Nutrition, participants who took 250 mg daily of holy basil extract for 8 weeks had significantly lower hair cortisol concentrations than the placebo group. Hair cortisol reflects long-term hormonal output over weeks, not just a single moment, so this is a meaningful finding. The holy basil group averaged about 270 pg per 50 mg of hair, compared to roughly 790 pg in the placebo group.
The same study also measured cortisol in real time after exposing participants to a lab-based stressor. Those taking holy basil had significantly lower salivary cortisol, lower blood pressure, and lower subjective stress ratings for up to 40 minutes following the stressor. Previous trials used higher doses of 600 to 1,200 mg daily, but this study found anti-stress effects at just 250 mg per day, suggesting it may be effective at lower doses than once thought.
Rhodiola Rosea
Rhodiola rosea targets what’s called the cortisol awakening response, the spike in cortisol your body produces in the first 30 to 60 minutes after waking up. In a 28-day randomized trial of people with stress-related fatigue, those taking a standardized rhodiola extract had a significantly blunted cortisol response to waking compared to placebo. They also performed better on attention tests and reported less mental fatigue.
Rhodiola tends to work faster than other adaptogens. A 12-week burnout trial found symptom relief in as little as one week, with continued improvements over time. Experts recommend starting at a lower dose and not exceeding 12 weeks of continuous use, since that was the longest trial duration studied. If you take antidepressant medications, use rhodiola with caution due to potential interactions.
Bacopa Monnieri
Bacopa is better known for its effects on memory and cognition, but it also appears to reduce cortisol. In a double-blind, placebo-controlled crossover study, acute doses of 320 mg and 640 mg of bacopa extract reduced salivary cortisol levels during a stressful multitasking test. Participants also reported positive mood effects. The researchers noted these results point to a physiological mechanism behind bacopa’s stress-reducing properties, though they flagged the need for larger studies to confirm the size of the effect.
Bacopa’s cortisol evidence is thinner than ashwagandha’s or holy basil’s. It’s a reasonable option if you’re also interested in cognitive benefits, but it shouldn’t be your first choice if cortisol reduction is the primary goal.
Reishi and Cordyceps Mushrooms
Functional mushrooms like reishi and cordyceps are often marketed as cortisol-lowering supplements, but their evidence is more nuanced. In a three-month study of endurance cyclists, a combination of reishi and cordyceps supplementation changed how the body’s cortisol system responded to intense exercise. Athletes taking the mushrooms had a smaller cortisol spike after racing (a 1.6-fold increase versus a 2.2-fold increase in the placebo group), suggesting the supplements helped buffer the stress response during extreme physical demand.
That said, baseline cortisol levels didn’t consistently drop in these athletes. The mushrooms appeared to modulate the cortisol response rather than suppress it outright. This is a useful distinction: reishi and cordyceps may help prevent exaggerated cortisol surges during physical or mental stress without lowering your resting levels. If you’re dealing with chronic psychological stress and elevated baseline cortisol, ashwagandha or holy basil have stronger direct evidence. Note that reishi has been associated with bloody stools with prolonged use of three to six months, and cordyceps should be used cautiously by anyone with an autoimmune condition.
How Long They Take to Work
The timeline varies by herb and what you’re measuring. Rhodiola can produce noticeable improvements in stress symptoms within one week, though cortisol changes in that study were measured at 28 days. Ashwagandha trials typically run 8 to 12 weeks before assessing cortisol. Holy basil showed significant cortisol reductions at the 8-week mark. Bacopa produced acute cortisol changes on the same day it was taken, but its long-term effects on baseline cortisol haven’t been well studied.
As a general rule, expect to use any of these herbs consistently for at least four weeks before drawing conclusions about whether it’s working. Hair cortisol testing, which reflects your average levels over one to two months, is a more reliable indicator of long-term change than a single blood or saliva test.
Safety Considerations
Adaptogens are generally well tolerated in healthy adults at studied doses, but several have meaningful interactions with medications. Ashwagandha can increase thyroid hormone activity and amplify the effects of sedating drugs. Rhodiola may interact with antidepressants. Ginseng and schisandra (two other adaptogens sometimes recommended for stress) can affect blood sugar and blood pressure, making them risky for people with diabetes or cardiovascular conditions. Astragalus and cordyceps stimulate the immune system, which could theoretically worsen autoimmune diseases.
If you’re taking prescription medications, especially for thyroid conditions, mood disorders, blood clotting, or blood sugar, check for interactions before adding any adaptogenic herb. Pregnant women should avoid ashwagandha entirely, and most adaptogens lack sufficient safety data in pregnancy.