Psilocybin Mushrooms

What it is

Three different things share the name psilocybin: the molecule, the mushroom that makes it along with many other compounds, and the material people handle, which may be dried mushroom, an extract or a purified powder. Most clinical trials use the purified molecule and most traditional use involves the mushroom, so a result for one does not automatically carry over to the others.

Psilocybin is a tryptamine, a chemical family that also includes serotonin. At least 144 mushroom species are thought to make it, and the most widely cultivated is Psilocybe cubensis [1]. The mushroom builds it with four enzymes, which were characterized in the laboratory in 2017, according to the abstract [3]. After it is swallowed, the body turns psilocybin into psilocin, the form that reaches the brain and acts [1] [7]. Psilocin is chemically fragile, and its oxidation fits the blue color of a bruised mushroom [1]. The mushrooms also contain related compounds, norpsilocin, baeocystin, norbaeocystin and aeruginascin [2], and whether they change what the mushroom does to a person is one of the central open questions on this page.

What is known

The short version. In screened healthy adults, psilocybin reliably changes perception, mood and the sense of self for about five to six hours. A few small, carefully run trials report that volunteers later rated the session as deeply meaningful and that the personality trait Openness rose in those who had a complete mystical-type experience, but most other measures did not change, and a larger placebo-controlled trial in healthy adults did not reproduce the Openness rise. Studies of very small repeated amounts mostly find no benefit over placebo. Whether the whole mushroom differs from the purified molecule in people has hardly been tested, and we found no registered trial of the whole mushroom at full-effect amounts in healthy adults.

How the compound acts in the body

Psilocin acts mainly on the serotonin 2A receptor. In 1998 ketanserin, a drug that blocks that receptor, reduced the effects of psilocybin in healthy volunteers, and larger amounts reduced them more [5]. Brain scans of eight healthy volunteers showed psilocybin occupying up to 72 percent of these receptors, and occupancy tracked the intensity of the experience more closely than blood levels of psilocin did (R-squared 0.81 against 0.35). The scan had no placebo, the volunteers knew they were receiving psilocybin, and five of the eight had used psychedelics before [6].

In healthy participants subjective effects lasted 5.5 to 6.4 hours on average [7]. Laboratory work with human enzymes and tissue, not measurements in living people, points to clearance by attaching a sugar molecule to psilocin, which the authors infer is done by UGT1A10 and UGT1A9 [8]. We found no human study tying a gene variant to the strength of a psilocybin experience.

The Johns Hopkins studies in healthy volunteers

The first study enrolled 36 adults who had never used a hallucinogen and took part regularly in religious or spiritual activities. Each received psilocybin in one double-blind session and methylphenidate, a stimulant, in another. Two months later the volunteers rated the psilocybin session as personally meaningful and spiritually significant, and of the 24 who completed that questionnaire 67 percent placed it among the five most meaningful experiences of their lives, while personality and general mood scales did not differ between the substances. Blinding was imperfect, since monitors misjudged 23 percent of sessions, and 11 of the 36 (31 percent) reported strong or extreme fear at some point [9].

At 14 months 58 percent still placed the session among the five most personally meaningful experiences of their lives, a retrospective self-rating. Of eight questionnaires only one, mystical experience, differed from screening, and in the analysis of all 36 no personality domain changed, Openness included, in volunteers who began well-adjusted and high in Openness and spirituality, leaving little room to change [10].

A dose-response study of 18 adults, 17 of them new to hallucinogens, gave each volunteer five eight-hour sessions with two monitors present and about eight hours of preparation, one placebo and four at rising amounts. At the two highest amounts 72 percent had a mystical-type experience, seven of the 18 (39 percent) had extreme fear at some point, six at the highest amount, and eight (44 percent) had paranoid or delusional thinking, seven at the highest amount. Systolic blood pressure rose to between 166 and 187 in four volunteers at the highest amount and was not treated. The authors state that the results should not be read as showing that casual use of a high amount is safe [11].

A third paper pooled the high-intensity sessions of both studies in 52 volunteers, all new to hallucinogens and above the population average in Openness at the start. Openness rose by 2.8 points on average (p = 0.023) and by 5.7 points among the 30 who had a complete mystical-type experience, a grouping made from what they reported after the session, so not a randomized comparison, with no correction for the number of tests. At about 16 months that group remained 4.2 points above baseline, only just at the conventional threshold (p = 0.050) and not significantly different from the first follow-up (p = 0.12). The other four domains did not change significantly [12].

The Openness finding has been tested once since, in a randomized, double-blind, placebo-controlled trial in 89 healthy adults, a secondary analysis of a phase 1 trial sponsored by COMPASS Pathways. Openness did not differ from placebo 8 or 85 days after psilocybin at two amounts, and neither did any other personality domain or symptom score, with every confidence interval including zero [47]. The authors note that 37 percent had used psilocybin before, that the sample may be too small and that volunteers could often tell what they had received. Self-rated changes in values were larger after psilocybin than placebo, but that questionnaire asks about change since the experience, so it is open to memory bias, and the analyses are exploratory [47]. An earlier open-label pilot of 12 healthy volunteers, with no placebo, found lower negative mood a week after one session, back toward baseline by one month, and no Openness change [48].

These studies show that a single supervised session can leave a strong impression, but not that it improves well-being, creativity or behavior in healthy adults generally: the samples were small, hand-picked and spiritually inclined, the outcomes mostly self-ratings, and no controlled follow-up ran past about 16 months.

When the amount is very small

Microdosing, repeatedly taking amounts too small to change perception, has disappointed in controlled studies. In a self-blinding citizen-science study of 191 people, mostly using LSD or an analogue and about a quarter psilocybin mushrooms, the microdosing group improved on several measures, including well-being, mindfulness and, within the group, Openness, but the placebo group also improved on mindfulness, paranoia and neuroticism, no measure differed between the groups at weeks 5 or 9, and the study may have lacked power to detect small differences. The substances were not verified, and most participants already supported psychedelic use [22].

A double-blind placebo-controlled trial of 34 healthy adults used whole Psilocybe cubensis mushrooms. The volunteers were not new to psychedelics, all planned to start microdosing, and psilocybin content was estimated from a pooled sample. Acute effects were stronger for the active material only in participants who guessed their condition correctly. Theta activity with the eyes closed was lower, signal complexity did not change, and there was no evidence of better well-being, creativity or cognition [23]. Two double-blind truffle trials found no reliable effect after correcting for multiple comparisons [24]. A 2026 meta-analysis of 24 studies (3,681 participants) found minimal effects on cognition, creativity or sustained mood in the randomized trials, with a pooled difference from placebo in depressive symptoms of -0.19 (95 percent interval -0.56 to 0.19), no difference in anxiety, and only two parallel trials behind those estimates. Observational studies reported improvements that the authors linked partly to expectation [25].

Blinding and expectation

Psilocybin is hard to hide. In a randomized trial of 120 healthy volunteers given psilocybin, MDMA or methylphenidate, blinding was insufficient overall, and psilocybin had the highest rate of participants working out what they had received [21], which lets expectation inflate self-rated outcomes. In an exploratory analysis of 55 patients with depression (a clinical group), expectation predicted response to escitalopram but not to psilocybin, though the authors caution that finding no link is not proof that expectation plays no part [49].

The whole mushroom compared with the molecule

A 2026 peer-reviewed narrative review in Biomolecules, with no formal systematic search, judged naturally derived psilocybin against six criteria. It finds perceived benefits widely reported, evidence of causal efficacy mixed and safety favorable but dependent on context, and states that "some preliminary preclinical evidence indicates possible entourage effects, but human validation is lacking" [1]. The "entourage effect" is the idea that minor compounds in the mushroom modify or amplify what psilocybin does.

The underlying studies are mixed. In female mice, abdominal injections of extracts of two wild mushroom species and of pure psilocin all produced the head-twitch response, a marker of serotonin 2A receptor action, and the authors concluded that the extracts acted synergistically, but their own toxicity table shows pure psilocin was more toxic than either extract, and the claim depends on an assumption about the extracts' active content that the paper does not detail [27]. A mouse study matching an extract and synthetic psilocybin by psilocybin content found no difference in the twitch response, did not test the extract against psilocybin directly, found no metabolite difference after correction for multiple testing, and states that the data do not show therapeutic superiority. Several authors hold roles at the companies that supplied the extract, and one has filed a patent application based on it [28].

On the minor compounds, baeocystin alone did not produce twitches in mice, although its breakdown product norpsilocin is a potent receptor activator in cell tests [29]. In a rat and test-tube study only psilocybin produced twitches, and norbaeocystin reduced immobility in a forced-swim test like psilocybin but only just (p = 0.05), in 10 male rats per group. The work was partly funded under a research agreement with PsyBio Therapeutics, one author holds substantial shares in it, several are named on patent applications, and this account rests on the preprint [30]. A computer-only study of 15 mushroom compounds predicted favorable absorption for eight, but psilocybin, baeocystin, norbaeocystin and aeruginascin themselves were not predicted to cross into the brain, and its conclusion of greater efficacy of whole extracts cannot follow from a prediction of binding [31]. In ChEMBL, release 37, baeocystin has a single head-twitch entry with no numeric value, norpsilocin (CHEMBL4648350) has nine activity records, and norbaeocystin and aeruginascin have none [34], so the reference data are sparse, which says nothing about whether those compounds are active.

Human evidence is close to absent. The single published report involving more than one form is an interview study, not a trial. Four patients in an end-of-life distress program in Canada had received synthetic psilocybin, whole mushroom and an extract on separate occasions and were interviewed about 19 months after their first session. All described every form as therapeutic, noted differences in vividness and feelings of sacredness, and preferred the whole mushroom. Nothing was blinded, the amounts were not matched, and a preference for something natural is itself a possible source of expectation, so any difference cannot be attributed to the material. One author holds a majority stake in MycoMedica Life Sciences, a company developing therapeutic psilocybin, and another is a paid consultant to it [26]. The Biomolecules review describes this report once as broadly similar and once as showing no difference, and neither matches the report's own account [1] [26].

Whole mushroom is now being given in registered trials, all in clinical populations: obsessive-compulsive disorder at the University of Arizona (NCT07347405), which lists "healthy volunteers: no" [35], a Brazilian depression pilot (NCT06898606) whose "accepts healthy volunteers" field says yes, which its own eligibility criteria contradict [36], and a PTSD trial sponsored by the Scottsdale Research Institute (NCT07275970) [37].

How much the material varies

"The mushroom" is not one material. A 2026 laboratory study grew 14 strains of P. cubensis under identical conditions. Total tryptamines ranged from 2.62 to 20.65 mg per gram of dried material, a spread of more than 7.8-fold, and psilocybin alone from 2.03 to 19.60 mg per gram, about 9.7-fold by the reported means. Strain names came from suppliers and appearance, and DNA sequencing (ITS) confirmed the species but cannot tell strains apart. Each strain's headline figure came from one pooled powder, and for six strains also measured in single fruiting bodies the two sets of means differed in every one, by up to 2.1-fold (13.53 against 6.43 mg per gram), so some of the spread between strains may be spread between samples [2].

The Biomolecules review gives 0.2 to 5.3 mg per gram, described as 25-fold, while its own table of species runs from 0.01 to 3.04 percent of dry weight, so its figures do not agree [1]. Wider ranges from community laboratories are not relied on here.

Standardization is possible but imperfect. Dried P. cubensis homogenized in Jamaica averaged 1.14 percent psilocybin plus psilocin by weight and held stable in capsules for 11 months, but batches still varied [32]. A validated method for 26 psychedelic compounds recovered psilocybin and psilocin well (about 88 to 99 percent in the simulated product) but norbaeocystin and harmaline out of range, and three authors work for the commercial laboratory that did the work [50].

A 2023 genome study of 38 wild isolates and 86 commercial cultivars found low genetic diversity among the cultivars, in five groups, and for 60 of the 124 genomes the psilocybin gene cluster had no variable site. The paper did not measure chemistry, and two authors own a company that grows psilocybin mushrooms for medicinal production [33]. Cultivars that are genetically close yet differ widely in chemistry is therefore a reading across [33] and [2], which did not study the same strains.

What is not known

Most of what the field knows about psilocybin was learned in other populations with a different aim. These open questions matter most for healthy adults.

Whether the whole mushroom differs from the purified molecule in people is the first open question. We found no blinded, matched-exposure comparison in any population, and the registered whole-mushroom trials enroll diagnosed patients. Whether the minor compounds interact in people is untested, since animal and computer studies point in different directions. Among 52 registry records returned by one search on 2 October 2026 we found no controlled trial giving whole mushroom at full-effect amounts to healthy adults, and a second search on 4 October 2026, limited to 15 records marked as accepting healthy volunteers, also found none by titles and intervention names, though the form of the material was not checked in every record. These searches were not exhaustive.

Whether the earlier lasting-effect findings, from fewer than 60 selected people per study with no controlled follow-up beyond roughly 16 months, occur in unselected healthy adults, whether they come from the drug or from setting and expectation, and how long they last are all unknown, and the one placebo-controlled trial of 89 healthy adults that measured personality did not reproduce the Openness rise. Surveys link emergencies to poor mindset and setting only as associations.

Sex, hormones and genes remain almost unstudied as influences on response. A registered protocol, the PsiMenis trial, will test whether menstrual cycle phase changes the response to a low amount in healthy menstruating people, with no results in the record we read [38]. The true rate of rare harms is also unknown, since persisting perception disturbance and psychosis appear uncommon in the controlled data but those samples number in the low hundreds, exclude people at higher risk, and surveys cannot give true rates.

The material itself is a last gap. Most studies above report amounts of psilocybin or mushroom with no measurement of what else the sample contained. For any human work, Metanoia's research is organized around four record-keeping standards: what the material was, what exposure occurred, the surrounding context, and the outcome, with an outcome measure addressed to the twelve dimensions of human potential still in development. None of that infrastructure is built for this substance yet.

Safety in healthy adults

This section summarizes what the literature reports about harms, by population and condition. It is not a statement that psilocybin is safe.

The Basel pooled analysis of three earlier trials covered 85 healthy participants aged 25 to 55 across 113 supervised single sessions. Psilocybin raised blood pressure and heart rate moderately and temporarily: heart rate peaked above 100 beats per minute in 7 percent of sessions, systolic blood pressure exceeded 140 in half of them with no reading above 180, and body temperature above 38 degrees Celsius became more frequent as the amount rose. Headache occurred in 55 percent of participants within 12 hours (30 percent after placebo) and nausea in 39 percent (2 percent after placebo), and no serious adverse reactions occurred. Participants were screened to exclude psychiatric and physical illness, were paid and were supervised in a hospital room, almost half (48 percent) had used a psychedelic before, and some also received other substances, such as LSD or mescaline, in other sessions [14]. An earlier study of eight healthy people found no change in electrocardiogram or temperature [15].

The most common risk in the moment is acute distress. In the Basel analysis only the higher amounts raised anxiety, no panic attacks or acute suicidality occurred, verbal support was enough, and afterward 87 percent rated the experience positive and 2 percent disappointing or bad [14]. A Zurich pooled analysis of 110 healthy people in eight placebo-controlled studies found strong dysphoria or anxiety, sometimes panic, only at the two highest amounts, all managed by support, with no later drug abuse, persisting perception disorder or prolonged psychosis [13]. These were also screened volunteers.

Brief returns of drug-like perceptions, called flashbacks, occur in some people. A pooled analysis of 142 healthy participants in six controlled studies (90 received only LSD, 24 only psilocybin and 28 both) found that 13 (9.2 percent) reported some flashback, typically visual and lasting seconds. Two found it distressing, and none met the criteria for hallucinogen persisting perception disorder (HPPD). One volunteer reported about 30 visual flashbacks over seven months, and one distressing case began 17 days after a psilocybin session that followed two days of escitalopram, which she interpreted as psychosis, developing panic attacks. Some participants had also received other substances [16]. In the Basel analysis 5 of 85 (6 percent) reported flashbacks, four a single episode 10 to 72 hours after the session and one, who had also received LSD, recurring visual flashbacks over several months that were not disturbing [14] [16]. These samples were small and screened, and HPPD may still occur at lower rates.

Surveys show a wider picture and carry heavier bias. In the Global Drug Survey 2017, 9,233 of 12,534 past-year mushroom users answered a question about emergency treatment, and 19 (0.2 percent) had sought it, with younger age the only predictor in a mostly young male sample. Most had anxiety, panic or paranoia, but 37 percent lost consciousness, 26 percent had seizures and 8 of the 19 (42 percent) were admitted to hospital [19]. In an internet survey of 1,993 people recruited because they had had a frightening "bad trip", 24 percent of the 1,339 whose experience was over a year earlier reported a psychological symptom lasting a week or more, 10 percent a year or longer, and 7.6 percent had sought treatment, while only 2.7 percent had a trusted, sober, experienced guide with them. The authors describe three cases that appeared linked to persisting psychotic symptoms and three suicide attempts, yet 84 percent said they had benefited, and participants were self-selected and unverifiable [18]. A US household survey of 130,152 adults (2001 to 2004) found lifetime psychedelic use not associated with higher rates of any mental health problem measured, but it was cross-sectional, its comparisons were not corrected for multiplicity, and an absence of association does not rule out harm in some people [20].

A 2008 guidelines paper for researchers, not a trial, excludes people with a personal or close family history of psychotic disorders or bipolar disorder, because hallucinogens may precipitate prolonged psychosis in people already vulnerable, and people on certain medicines, since lithium and tricyclic antidepressants can intensify the effects, as can acute use of serotonin-reuptake inhibitors, while chronic use of those and of MAO inhibitors can blunt them [17]. In a survey of 611 people who combined mushrooms with SSRI or SNRI antidepressants, roughly half reported weaker effects [1]. The Arizona registry record adds cardiovascular disease, pregnancy and recent substance use [35]. The safety data above therefore say little about people with those conditions or about older adults, and none of this assesses any medicine.

The mushroom itself adds risks that come from the organism, including misidentification of species, variable potency, contamination, and rare syndromes such as wood-lover paralysis, a syndrome of muscle weakness [1]. Given the variation described above, the psilocybin content of an individual piece of mushroom is unknown unless it has been measured.

Legal status

Each entry names the jurisdiction, the official source and the date read, 2 October 2026 except where stated. Oregon and Colorado were rechecked on 4 October 2026, Oregon from an archived copy and Colorado from initiative text and agency documents. Other jurisdictions are not covered, and none of this is legal advice.

United States, federal. Psilocybin and psilocyn (psilocin) are Schedule I controlled substances, listed at 21 U.S.C. 812(c), Schedule I(c), items 15 and 16 [39]. The regulation, 21 CFR 1308.11(d), items 29 and 30, applies to "any material, compound, mixture, or preparation" containing any quantity of them, with DEA codes 7437 and 7438 [40]. Schedule I rests on three statutory findings, a high potential for abuse, no currently accepted medical use in treatment in the United States, and a lack of accepted safety under medical supervision [39]. FDA's 2026 novel drug approvals list, updated 28 September 2026, contains no psilocybin product [41].

Oregon. Ballot Measure 109 is codified as ORS chapter 475A, the Oregon Psilocybin Services Act, which voters approved in November 2020 according to the Oregon Department of Revenue [51]. Licensing applications opened on 2 January 2023 and the first service centers in summer 2023 [42] [43]. The act is framed for people 21 and older, bars the Authority from requiring a diagnosis, lets cities and counties refer ordinances to their voters, and may not be construed to exempt anyone from federal law [42]. The statute was read from an archived copy of the legislature's page captured on 12 September 2026, because the live site did not respond on 2 or 4 October. It is the 2025 edition, and a notice says sections were amended or repealed in the 2026 regular session, which we did not read, so the sections described here may differ from current law.

Colorado. Colorado's program began with the Natural Medicine Health Act, approved by voters in November 2022 as Proposition 122, by 1,296,992 votes to 1,121,124 in the Secretary of State's official results [52]. The initiative text acknowledges that the substances remain prohibited under federal law and sets up licensed healing centers and facilitators and, separately, protection from state and local penalties for defined personal-use acts, with sale excluded [44]. A 2026 law, HB 26-1325, signed in June 2026, took effect on 12 August 2026 according to the Natural Medicine Division's documents, which describe it as amending the natural medicine code and the personal-use provisions of the criminal code [45]. We read the Division's summaries and not the law's text, so its provisions are not described here, and the initiative text is the filed ballot text and not the current codified statute, so the description may no longer match current law. The Division's FAQ says the sale of any natural medicine is prohibited, which concerns personal use and not the regulated program, and may be out of date [45].

Both state programs run alongside the federal listing, and the Oregon statute and the Colorado initiative text each acknowledge that federal law still applies [40] [42] [44].

History and tradition

Grade 4 sources (traditional and ethnographic), relayed in part by one peer-reviewed review that is grade 1 as a publication. These describe what traditions practice and what early reports said. They are not evidence that any use works.

The mushrooms have a long recorded history in Mesoamerica. A 16th-century Spanish friar, Bernardino de Sahagún, called them drunken mushrooms [46]. Contemporary ethnography documents continuing ceremonial and healing use among the Mazatec and other peoples [1]. In the Mazatec velada, a night-long gathering, illness can mean a displaced or attacked spirit and the mushroom acts as an agent of diagnosis and repair [1], a frame that differs from personal growth in a healthy adult.

R. Gordon Wasson's 1957 account in Life magazine of a Mazatec ceremony is described by later scholars as displacing ceremonial use and spreading recreational use [46]. In 1958 Albert Hofmann and colleagues isolated psilocybin and psilocin, and psilocybin was soon synthesized [2] [4]. The 2026 review quotes, as historical context only, Hofmann's report that the healer María Sabina judged synthetic psilocybin pills as powerful as the mushrooms [1].

A 2025 study of 30 people in one Zapotec community, reached by referral from known users and recording a single species, found healing and divination uses continuing but declining. Interviewees link this to climate change and deforestation, although the rainfall figures did not show a significant drop, and the authors stress that practices cannot be generalized from one Zapotec place to another [46].

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