Reishi mushroom shows early promise for anxiety relief, but the evidence is still limited. A small randomized trial of 48 breast cancer patients found that four weeks of reishi powder significantly reduced anxiety, depression, and fatigue compared to placebo. Beyond that, most of the supporting data comes from animal studies, surveys, and trials focused on related outcomes like sleep and mood rather than anxiety specifically.
That said, there are plausible biological reasons reishi could help, and many people report feeling calmer after taking it. Here’s what the science actually shows so far.
How Reishi May Affect the Brain
Reishi contains over 130 different triterpene acids, a class of compounds responsible for many of the mushroom’s medicinal properties. In animal studies, these triterpenes appear to work primarily through the serotonin system rather than the GABA pathway that most conventional anti-anxiety medications target. When mice were given reishi extract, researchers found that serotonin levels in the brain increased significantly, while levels of GABA, norepinephrine, and dopamine stayed the same.
The mechanism involves the gut. Reishi’s triterpenes influenced gut bacteria in ways that activated genes in the serotonin signaling pathway, specifically boosting production of the enzyme that converts tryptophan (an amino acid from food) into serotonin. When researchers wiped out the gut bacteria with antibiotics, the effects disappeared. This suggests reishi needs a healthy gut microbiome to produce its calming effects, which is a detail worth noting if you’re also taking antibiotics or have digestive issues.
Since serotonin regulates both mood and sleep, this single pathway could explain why people report feeling both calmer and sleeping better on reishi.
What Human Studies Show
The direct evidence for anxiety reduction in humans is thin but encouraging. The strongest result comes from a pilot trial where 48 breast cancer patients undergoing hormone therapy took reishi powder for four weeks. Compared to placebo, the reishi group had significant improvements in anxiety, depression, fatigue, and appetite loss.
A separate study tested reishi in 64 women with fibromyalgia over six weeks. While the reishi group didn’t beat placebo by a statistically significant margin after corrections for multiple comparisons, within-group improvements told an interesting story. Women taking reishi saw meaningful gains in happiness scores and life satisfaction, and their depression scores dropped from an average of 7.6 to 5.4. The placebo group showed no such trend. When researchers calculated how many people needed to take reishi for one person to benefit, the number was three for life satisfaction and four for depression, which are reasonable response rates for a supplement.
In a cross-sectional survey of cancer patients using reishi, about half reported clinically meaningful improvements in depression and drowsiness. Anxiety wasn’t among the top five symptoms that improved in that survey, though it was measured.
The Sleep Connection
Much of reishi’s reputation for calming anxiety may come indirectly through better sleep. Poor sleep amplifies anxiety, and anxiety disrupts sleep, creating a cycle that’s hard to break. Reishi appears to promote sleep through its effect on serotonin production in the brain, and improved sleep alone can meaningfully lower daytime anxiety levels.
People who take reishi commonly report noticing sleep improvements before other benefits. Relaxation and better sleep quality tend to appear within the first one to two weeks of daily use, while broader effects on energy and immune function typically take longer, around two to four weeks.
Effects on Stress Hormones
One small study examined cortisol levels in endurance cyclists who took a combination of reishi and cordyceps mushroom supplements for three months. In well-trained athletes, resting cortisol dropped from 11.7 to 7.5 nanograms per milliliter after supplementation. In overtrained athletes at risk of burnout, the supplements appeared to normalize their cortisol response to exercise, preventing the exaggerated spike seen in the placebo condition (a 1.6-fold increase versus 2.2-fold).
These results are intriguing but very preliminary. The study involved only seven athletes total and used a combination supplement, so it’s impossible to attribute the cortisol changes to reishi alone.
How Long Before You Notice Results
Reishi isn’t fast-acting in the way that a medication like a benzodiazepine is. You won’t feel a noticeable shift after a single dose. Most people who respond to reishi report subtle improvements in calmness and sleep quality within the first few days to two weeks of consistent daily use. The breast cancer trial that showed anxiety reduction used a four-week protocol, which is a reasonable minimum timeframe to evaluate whether it’s working for you.
Longer-term benefits related to immune function and overall well-being generally require at least a month of regular use.
Safety and Potential Risks
Reishi is generally well tolerated, but it’s not risk-free. The most concerning reports involve liver damage. Multiple case reports have documented hepatitis in people taking reishi powder, including one fatal case where a patient switched from traditionally boiled reishi tea to concentrated powder. In one case, a man developed significantly elevated liver enzymes just two days after taking reishi powder alongside alcohol. Interestingly, reishi has also shown liver-protective effects in other contexts, so the relationship is complex and may depend on the preparation method, dose, and individual health factors like pre-existing liver conditions or alcohol use.
Reishi also interacts with several categories of medications. It can increase bleeding risk if you’re taking blood thinners. It may boost immune activity, which is a problem if you’re on immunosuppressant drugs. And in lab studies, reishi inhibits certain liver enzymes that metabolize many common medications, potentially altering how quickly your body processes those drugs. If you take prescription medications, this is worth discussing with a pharmacist or doctor before adding reishi to your routine.
The Bottom Line on Reishi and Anxiety
Reishi has a plausible mechanism for reducing anxiety through serotonin production and gut microbiome changes. One small clinical trial directly supports anxiety reduction, and several others show related benefits for mood, depression, and sleep. But the overall body of human evidence is still small, and no large-scale trials have specifically targeted anxiety as the primary outcome.
If you’re dealing with mild, everyday anxiety and are curious about reishi, a four-week trial of a reputable extract is a reasonable approach. For moderate to severe anxiety that interferes with daily life, reishi shouldn’t replace evidence-based treatments, though it could potentially complement them, provided there are no medication interactions.