The Stamets Stack adds two compounds to a psilocybin microdose — Lion’s Mane mushroom (Hericium erinaceus) and niacin (vitamin B3) — usually on a four-days-on, three-days-off schedule. The rationale is mechanistic and appealing: Lion’s Mane is linked, in laboratory work, to nerve growth factor, and the hope is that pairing it with psilocybin’s own plasticity-related effects might be synergistic. Two cautions run through this whole topic. First, the Lion’s Mane evidence is preclinical and about the mushroom alone, not the combination — and the niacin “distribution” story has no good support at all. Second, when stacking was actually examined in microdosers, adding Lion’s Mane and niacin made no overall difference to mood and mental-health outcomes. The stack is a plausible-sounding combination with high anecdotal popularity and, so far, no controlled evidence that the additions help.
What the stack is
The Stamets Stack is named for the mycologist Paul Stamets, who proposed combining a sub-perceptual psilocybin dose with two other ingredients. The first is an extract of Lion’s Mane, Hericium erinaceus, an edible mushroom. The second is niacin — vitamin B3 — typically in the form that produces a flush. The usual schedule is four consecutive dose days followed by three rest days, a slightly denser rhythm than the Fadiman 1/3/1. Combining a psychedelic microdose with non-psychedelic compounds in this way is what the community calls stacking, and survey work shows it is a common real-world practice, with Lion’s Mane and niacin among the most frequent additions. [1] Observational Adults who microdose psychedelics report health related motivations and lower levels of anxiety and depression compared to non-microdosers doi:10.1038/s41598-021-01811-4
It is worth separating the parts. The psilocybin is the active microdose, and everything the rest of this library says about microdosing applies to it unchanged. Lion’s Mane and niacin are the additions that define the stack, and they are where the specific claims — and the specific evidence problems — live.
The Lion’s Mane rationale: real, preclinical, and about the mushroom alone
The case for Lion’s Mane rests on nerve growth factor (NGF), a protein that helps maintain neurons and supports their growth. Laboratory studies have found that extracts of Hericium erinaceus can induce NGF: in one well-known experiment, the mushroom’s extract promoted NGF gene expression in human astrocytoma cells through a specific signalling pathway, and a short feeding study in mice raised NGF messenger RNA in the hippocampus. [2] Peer-reviewed Nerve growth factor-inducing activity of Hericium erinaceus in 1321N1 human astrocytoma cells doi:10.1248/bpb.31.1727 That is a genuine finding, and it is the seed of the synergy idea — psilocybin acts through the serotonin 5-HT2A receptor, and its downstream effects are thought to touch the brain’s plasticity machinery, including neurotrophic signalling and BDNF, [3] Peer-reviewed Psychedelics doi:10.1124/pr.115.011478 so a compound that nudges NGF might, in principle, complement it. The psilocybin side of that plasticity story is set out in neuroplasticity and BDNF.
Two qualifications keep this honest, and both are decisive. First, the Lion’s Mane NGF work is preclinical — cells and animals, not people taking the stack — and the gap between “induces NGF in a dish” and “improves a person’s life” is exactly the gap this library flags everywhere. [2] Peer-reviewed Nerve growth factor-inducing activity of Hericium erinaceus in 1321N1 human astrocytoma cells doi:10.1248/bpb.31.1727 Second, the finding is about Lion’s Mane on its own. It says nothing about what happens when the mushroom is combined with a psilocybin microdose and niacin; a result for one compound in isolation does not transfer to a three-part combination. [4] Peer-reviewed Microdosing psychedelics: More questions than answers? An overview and suggestions for future research doi:10.1177/0269881119857204 The synergy is a hypothesis layered on a preclinical result, not a demonstrated effect.
Combining plausible mechanisms does not multiply evidence. This is the error the stack invites. Each ingredient can carry its own scientific rationale — psilocybin’s plasticity story, Lion’s Mane’s NGF story — but pairing two plausible ideas does not add their evidence together into a stronger demonstrated outcome. A combination is its own intervention and has to be tested as one; two rationales sitting side by side are still two rationales, not a result. [4] Peer-reviewed Microdosing psychedelics: More questions than answers? An overview and suggestions for future research doi:10.1177/0269881119857204
The niacin “distribution” claim: unsupported
Niacin is the part of the stack to be most careful about, because the rationale usually offered for it does not hold up. The common explanation is that niacin — specifically the flushing form — aids the “distribution” of the other compounds through the body, sometimes with a suggestion that the flush itself is doing something useful.
This distribution claim has no good supporting evidence and should be treated as folk rationale, not mechanism. What niacin reliably does in this form is cause a flush: a temporary dilation of blood vessels producing skin reddening, warmth, and tingling. That is a real physiological effect, but it is not evidence that niacin improves the delivery or action of psilocybin or Lion’s Mane. The flush is also the stack’s main practical downside — many people find it uncomfortable. Including niacin is a convention with an unsupported justification attached; this page names the rationale precisely so it is not mistaken for an established mechanism.
The one direct test — and it was unsupportive
The most important piece of evidence is the one most often left out of enthusiastic accounts. A large observational study followed psilocybin microdosers and non-microdosing comparators for about a month and reported small-to-medium improvements in mood and mental health among the microdosers. [5] Observational Psilocybin microdosers demonstrate greater observed improvements in mood and mental health at one month relative to non-microdosing controls doi:10.1038/s41598-022-14512-3 Within that study, the researchers were able to compare microdosers who stacked Lion’s Mane and niacin against those who took psilocybin alone. The supplementary analysis found that adding Lion’s Mane and B3 did not change the mood and mental-health outcomes overall; the only hint of a difference was a small effect suggested among older respondents. [5] Observational Psilocybin microdosers demonstrate greater observed improvements in mood and mental health at one month relative to non-microdosing controls doi:10.1038/s41598-022-14512-3
That result deserves emphasis because it runs directly against the stack’s marketing. This was still an observational, unblinded design — it shares all the expectation problems of the broader literature, and it is one study — but it is the closest thing to a direct test of stacking that exists, and it does not support the idea that the additions help. [5] Observational Psilocybin microdosers demonstrate greater observed improvements in mood and mental health at one month relative to non-microdosing controls doi:10.1038/s41598-022-14512-3 Set alongside the systematic-review picture that microdosing’s effects beyond expectation remain unproven, [6] Systematic review The emerging science of microdosing: A systematic review of research on low dose psychedelics (1955-2021) and recommendations for the field doi:10.1016/j.neubiorev.2022.104706 the stack ends up as a more elaborate version of an already-unproven practice, with the extra compounds adding cost and, in niacin’s case, discomfort, but no demonstrated benefit.
Why convention treats it as “advanced”
Practitioner guidance usually positions the Stamets Stack as something to try only after a plain schedule, not as a starting point. The stated reason is methodological and, unusually, entirely sound: introducing two additional compounds at once means that if anything changes, you cannot tell which ingredient — if any — is responsible. The stack multiplies variables faster than it multiplies information. Whatever one concludes about microdosing in general, dosing one thing at a time is simply better self-experimentation, which is why the convention exists. [7] Observational Might Microdosing Psychedelics Be Safe and Beneficial? An Initial Exploration doi:10.1080/02791072.2019.1593561
- Three components
- A psilocybin microdose plus Lion’s Mane extract plus niacin, usually on a 4-on/3-off schedule; the latter two are the defining additions. [1] Observational Adults who microdose psychedelics report health related motivations and lower levels of anxiety and depression compared to non-microdosers doi:10.1038/s41598-021-01811-4
- Lion's Mane and NGF (preclinical)
- Lion’s Mane extract can induce nerve growth factor in cells and animals — a real finding about the mushroom alone, not about the stack, and not in humans microdosing. [2] Peer-reviewed Nerve growth factor-inducing activity of Hericium erinaceus in 1321N1 human astrocytoma cells doi:10.1248/bpb.31.1727
- The niacin 'distribution' claim is unsupported
- Niacin reliably causes a flush; the idea that it aids distribution of the other compounds is folk rationale without good evidence.
- Stacking showed no added benefit
- The one observational comparison of stacked versus unstacked microdosers found no overall difference in outcomes. [5] Observational Psilocybin microdosers demonstrate greater observed improvements in mood and mental health at one month relative to non-microdosing controls doi:10.1038/s41598-022-14512-3
- Plausible is not proven
- A mechanistic rationale and high anecdotal popularity are not a controlled demonstration; the stack has never been tested in a trial. [4] Peer-reviewed Microdosing psychedelics: More questions than answers? An overview and suggestions for future research doi:10.1177/0269881119857204 [6] Systematic review The emerging science of microdosing: A systematic review of research on low dose psychedelics (1955-2021) and recommendations for the field doi:10.1016/j.neubiorev.2022.104706
Frequently asked questions
What is the Stamets Stack?
It is a microdosing variation popularized by mycologist Paul Stamets that combines three things: a psilocybin microdose, Lion’s Mane mushroom extract, and niacin (vitamin B3). [1] Observational Adults who microdose psychedelics report health related motivations and lower levels of anxiety and depression compared to non-microdosers doi:10.1038/s41598-021-01811-4 It is usually run on a four-days-on, three-days-off schedule. The psilocybin is the active microdose; Lion’s Mane and niacin are the additions that distinguish the stack from a plain schedule. Combining a psychedelic microdose with other compounds in this way is what practitioners call “stacking”.
What is the rationale for adding Lion's Mane and niacin?
The rationale is mechanistic. Lion’s Mane is associated, in laboratory studies, with the induction of nerve growth factor, a protein involved in the maintenance and growth of neurons, and the idea is that pairing it with psilocybin’s own plasticity-related effects might be synergistic. [2] Peer-reviewed Nerve growth factor-inducing activity of Hericium erinaceus in 1321N1 human astrocytoma cells doi:10.1248/bpb.31.1727 Niacin is offered a “distribution” rationale — a claim that it helps move the compounds through the body — and that claim has no good support. It is important that this is a rationale for trying the combination, not evidence that the combination does anything.
Is there evidence the Stamets Stack works?
There is no controlled trial of the stack. The Lion’s Mane nerve-growth-factor findings are preclinical — from cells and animals — and concern the mushroom on its own, not the three-compound combination. [2] Peer-reviewed Nerve growth factor-inducing activity of Hericium erinaceus in 1321N1 human astrocytoma cells doi:10.1248/bpb.31.1727 The most relevant human data come from an observational study that directly compared microdosers who stacked Lion’s Mane and niacin with those who did not, and found no overall difference in mood and mental-health outcomes, with only a small effect suggested in older adults. [5] Observational Psilocybin microdosers demonstrate greater observed improvements in mood and mental health at one month relative to non-microdosing controls doi:10.1038/s41598-022-14512-3 So the rationale is mechanistic and the one direct comparison is unsupportive.
What does the niacin do, and why the flush?
Niacin in its flush-causing form produces a temporary reddening, warmth, and tingling of the skin as blood vessels dilate. Within the stack it is the most noticeable practical effect, and many people find it uncomfortable. The “distribution” explanation sometimes given for including it — that the flush helps deliver the other compounds — is folk rationale without good supporting evidence, and should be treated as unsupported rather than as a mechanism.
Is the Stamets Stack a good place to start?
Practitioner convention treats it as an advanced variation rather than a starting point, on the reasoning that adding two compounds at once makes it impossible to tell what, if anything, is responsible for any change you notice — it stacks variables as much as compounds. [7] Observational Might Microdosing Psychedelics Be Safe and Beneficial? An Initial Exploration doi:10.1080/02791072.2019.1593561 Whatever one thinks of microdosing generally, that methodological point is sound: more moving parts means less interpretable self-tracking. None of this is a recommendation to use any of these substances.