Does microdosing psilocybin work?

Disclosure up front: I run a functional-mushroom supplement company. Its products are mushrooms like lion's mane, not psychedelics, and it sells nothing containing psilocybin. Still, "mushrooms help your brain" is a category I have a stake in, so the full disclosure is at the bottom. This post is not a how-to, and nothing in it is a dosing suggestion.

Why the placebo matters so much here

Most early microdosing evidence came from surveys and open-label studies, where people knew what they were taking. That design has a known problem. Microdosers tend to be people who already expect it to work, and mood, energy and creativity are exactly the outcomes that move when you expect them to. A placebo arm is the only way to separate what the drug does from what believing in the drug does.

It's also unusually hard to run one. As the Imperial team behind the biggest trial points out, restrictive drug policies make placebo-controlled psychedelic studies difficult and expensive, especially for microdosing, which runs for weeks. So researchers got creative.

The biggest trial: participants blinded themselves

A team at Imperial College London, led by Balázs Szigeti, published a "self-blinding" study in eLife in 2021. People who were already planning to microdose followed online instructions to put their own microdoses into opaque capsules, mix them with identical empty capsules, and seal them into envelopes. Drawing envelopes put each person into one of three groups for a four-week dosing period: all microdose weeks, all placebo weeks, or half and half. Nobody knew which group they were in until the end.

Of 1,630 people who signed up, 240 started and 191 finished, which the authors describe as the largest placebo-controlled trial on psychedelics at the time. Most participants used LSD or an LSD analogue. About a quarter (57 people) used psilocybin mushrooms, at an average reported dose of 0.2 g of dried mushroom.

The result is the cleanest version of the placebo story. In the microdose group, every psychological measure improved from the start of the study to the end of the dosing period. But the placebo group improved too, and there were no significant differences between the groups. On a few short-term measures (emotional state, drug intensity, mood, energy, creativity, and later anxiety) the microdose group did score a little better. The authors found those small differences could be explained by participants breaking the blind, meaning correctly guessing they'd had a real dose.

The paper is candid about its limits. It calls the design part-controlled and part-observational: better than a survey, weaker than a clinical trial. Participants supplied their own drugs, so nobody measured the actual dose. And the sample was mostly educated men from Western countries with positive views of psychedelics, which is the group most likely to expect a benefit.

The mushroom trial: the effect was real, and so was the guessing

A smaller study focused on psilocybin mushrooms alone. Federico Cavanna and colleagues in Buenos Aires published it in Translational Psychiatry in 2022, registered in advance as NCT05160220. They recruited 34 people who were about to start microdosing with their own Psilocybe cubensis. Each person did one week on 0.5 g of dried mushroom and one week on a placebo capsule of the same weight made from an edible mushroom, in random order, with a week off between. Neither participants nor researchers knew which week was which until the analysis was done.

The authors call 0.5 g the upper range of what microdosers use. A lab tested pooled samples and the team estimated an effective dose of roughly 0.9 mg of psilocybin, with a caveat I appreciate: individual doses could have been higher or lower depending on whose mushrooms they were. Mushroom products vary, which is a recurring theme on this beat (see Report 129 for the lion's mane version).

Here's what they found. The microdose did something. People rated its acute effects as more intense than placebo on dosing days, and EEG showed reduced power in the theta band. But on creativity, cognition, physical activity and self-reported well-being, there was no benefit. The few small differences that showed up leaned toward worse performance on two attention tasks, not better.

Then the key detail. Participants correctly guessed which week was which in 49 of 64 measurement weeks, or 75%. When the team split the data, the stronger acute effects showed up only in the people who guessed right. In the people who stayed fooled, the evidence was inconclusive either way; the authors say that group was likely too small to settle it. Their conclusion is careful: expectation "underlies at least some" of the benefits people attribute to microdosing.

A newer pair of trials points the same way

Prochazkova and colleagues published two more randomized, double-blind, placebo-controlled trials of microdosing psilocybin truffles in Neuropharmacology (online October 2025, in the February 2026 issue). I could only read the abstract, so I'll stick to what it says. Microdosing did not significantly change behavioral or subjective measures compared with placebo. A few early effects on social cognition, mood and self-reported flexibility didn't survive correction for testing many outcomes at once. People in the active condition reported more negative bodily feelings. And unlike the earlier studies, the authors report that participants stayed effectively blinded throughout.

The fair counterargument

It would be easy to stop at "microdosing is a placebo." Two researchers who've reviewed the whole field argue that's premature, and their case deserves a hearing.

Vince Polito and Paul Liknaitzky published a rapid review in the Journal of Psychopharmacology in 2024. They found 19 placebo-controlled microdosing studies of LSD or psilocybin. Across them, microdoses did produce changes relative to placebo in brain activity, physiology, subjective experience, mood and cognition. They list eight reasons the placebo verdict is ahead of the evidence, including: few studies, small samples, signs of dose-dependent effects in LSD research, a narrow range of doses tested, and no studies in people with clinical conditions like depression. They also note that no psilocybin study had yet compared multiple doses. Their bottom line is that it isn't yet possible to say whether microdosing is a placebo.

I think that's a reasonable position, and it fits the trials. "The drug does nothing" is not what these studies show. Cavanna's EEG changes and the acute effects people noticed are real pharmacology. What the trials keep failing to show is the specific benefit people microdose for: better mood, sharper thinking, more creativity, above what an empty capsule delivers.

How I'd read it

The headline "microdosing is just placebo" overstates it, and so does "science shows microdosing works." The defensible version is narrower. In healthy volunteers, in the controlled trials so far, microdoses of psilocybin produce effects you can feel and measure, but they haven't beaten placebo on the well-being and cognition claims. And the effects you can feel may be part of the problem, because noticing the dose tells you which week you're in.

Two things I'd take from this beyond microdosing. First, a placebo group that improves isn't a failed study. It tells you the improvement is real but has another cause, which here looks a lot like expectation. Second, any trial of something people can feel should check whether participants figured out what they got. These teams asked. Polito and Liknaitzky found that only 12 of the 19 microdosing studies they reviewed checked participants' guesses at all.

What would change my read: a trial in a clinical population, a psilocybin study comparing several doses, or a large trial where the blind demonstrably holds and a benefit still shows up. If one lands, I'll update this post in place.

Not medical advice. This is educational analysis, not a recommendation — a study is not a prescription. Talk to a qualified clinician before acting on anything you read here. Full disclaimer →

Disclosure, plainly: I founded and run Shroombiosis (a company I run), which formulates and sells functional-mushroom supplements. It sells no psychedelic products, but I have a commercial stake in how people think about mushrooms and the brain. I have no relationship with the authors of these papers. Nothing here is sponsored and no link earns a commission; here's the full policy. A recommendation with no stake at all: for performance nutrition, Die Tryin Co. is a fellow combat-veteran-owned brand I'm glad to point people to. I don't own it and earn nothing from the link.