Does microdosing mushrooms work? What placebo-controlled studies found

The short answer

Not in a way placebo-controlled studies have been able to show so far. A 2026 meta-analysis of randomized trials in healthy adults found no significant effect on depression, anxiety or stress, and a 2026 umbrella review found that the only significant pooled effect was a small decrease in cognitive control.¹²

Microdosing means taking very low doses of a psychedelic such as psilocybin or LSD, typically repeated over a longer period of time.³ My Mushroom Dispensary, the online shop for adults 21+ run by the team that publishes this site, has a page on the microdosing effects people report. This page sticks to a narrower question: whether those effects hold up when researchers compare microdosing with a placebo.

How do placebo-controlled studies test microdosing?

In a placebo-controlled study, some participants unknowingly take a dummy capsule, so both groups expect the same thing and any difference can be put down to the drug. That only works if people can't tell which capsule they took, which turns out to be the hard part with psychedelics (see below).

The trials so far tested psilocybin mushrooms or truffles, LSD, or a mix of both, mostly in healthy adults. Even in a trial, the psilocybin content was an estimate: one team measured its pooled mushroom material and noted that the content per capsule "could have been higher or lower depending on the source."⁵ That's the same problem our potency data shows across published measurements, and it's why the milligram figure on a capsule label needs reading carefully.

What each placebo-controlled trial found

Two of these studies used LSD only, and one mixed LSD with mushrooms, so they speak to microdosing in general rather than to psilocybin specifically. The ADHD trial was funded by the drug developer Mind Medicine, according to the paper's funding statement.⁸

Can people tell when they've had the real thing?

Often, yes, and that complicates every result above.

• In Szigeti 2021, participants guessed their capsule correctly at a rate of 0.72, against 0.62 for someone guessing at random who knew there were three placebo capsules for every microdose, and 86% of those surveyed afterward said they'd thought about which capsule they had before being asked. Once those guesses were added to the analysis, the small short-term differences between microdose and placebo could be explained by people breaking the blind; only how strong the capsule felt stayed different.⁴
• In Cavanna 2022, participants correctly identified their condition in 49 of 64 measurement weeks, and the active capsule felt stronger than placebo only for people who had guessed right.⁵
• In Marschall 2022, guesses were no better than chance after the first block of the study but were after the second.⁶
• In the two Prochazkova trials, participants stayed blinded, and microdosing still made no significant difference.⁹

Not everyone reads this as proof of a placebo effect. A 2024 review by Polito and Liknaitzky identified 19 placebo-controlled studies and said that, taken together, they indicate changes in "neurobiology, physiology, subjective experience, affect, and cognition relative to placebo." It gave eight reasons why calling microdosing a placebo is premature, including small samples, few doses studied, doses that may have been too small, and only non-clinical participants. Its conclusion: "it is not yet possible to determine whether microdosing is a placebo."¹¹

What the 2026 reviews concluded

Meshkat 2026 reviewed 24 studies with 3,681 participants in healthy adults, of which 6 fed into meta-analyses. Pooling two parallel-group randomized trials (117 participants), it found no significant effect on depressive symptoms (standardized mean difference -0.19, 95% confidence interval -0.56 to 0.19), anxiety (-0.20, -1.11 to 0.71) or stress (0.02, -0.39 to 0.43). Each interval crosses zero, meaning no clear effect either way. Adverse event risks were similar with microdosing and with placebo.¹

Özaydın 2026, an umbrella review of 3 meta-analyses drawing on 14 studies (1,614 participants in 13 samples), found "the sole significant pooled effect was a small decrease in cognitive control" (d = -0.34, 95% CI -0.62 to -0.06). It concluded that self-reported mood benefits "are largely attenuated under placebo-controlled conditions."²

Why do some studies report benefits?

The large positive studies didn't use a placebo. Rootman 2021 compared 4,050 microdosers with 4,653 non-microdosers using data from a mobile app; 85% of the microdosers used psilocybin. Among people reporting mental health concerns, microdosers reported lower depression, anxiety and stress.¹² A follow-up of 953 psilocybin microdosers and 180 comparison participants over about 30 days found "small- to medium-sized improvements in mood and mental health."¹³

The authors say both groups "were aware of their status from the onset," so expectancy effects are "impossible to rule out," and participants were self-selected.¹³ Their disclosures also matter: several authors are linked to the company behind the app, and one is an investor and a patent applicant for combinations of psilocybin, lion's mane and niacin.¹² These studies show what microdosers report, not what microdosing causes.

What isn't known about safety

Heart valves. Psilocin, the form psilocybin takes in the body, acts on the serotonin 5-HT2B receptor, a pathway known to drive drug-induced valve disease.¹⁴ A 2023 analysis found psilocin and LSD bind 5-HT2B at least as strongly as their main target, as partial agonists. Safety margins at typical microdosing blood levels were wider than for known valve-damaging drugs, "but not without potential risk," and no animal or clinical study designed to test valve risk was found.³ A 2026 systematic review of 17 studies on psychedelics and valve disease reported that "no studies were found on psilocybin, dimethyltryptamine or mescaline."¹⁴ The risk from months of repeated use hasn't been measured.

Side effects in the trials. In the LSD trial of 80 men, 4 of the 40 on LSD withdrew because of anxiety.⁷ The Prochazkova trials found more negative bodily feelings,⁹ and the umbrella review found a small drop in cognitive control.²

Medicines and mental-health history. Interaction risks still matter. In an analysis of online reports of classic psychedelics taken with lithium, 47% of 62 reports described seizures.¹⁵ Antidepressants, including MAOIs, raise other questions covered in our medication interactions reference. If you have a personal or family history of psychosis or bipolar disorder, read who should avoid psilocybin first. Don't stop or change a prescribed medicine on your own; talk to your prescriber or pharmacist.