Mescaline: what the research shows | The Psychedelic Library

Also known as Peyote (Lophophora williamsii), San Pedro cactus, 3,4,5-trimethoxyphenethylamine

At a glance

Type: Classic psychedelic (a phenethylamine), found in the peyote and San Pedro cacti.
How it acts: Activates serotonin 2A receptors, like psilocybin and LSD.
Approved uses: None.
Legal status: Schedule III in Canada, but peyote itself is excluded. Schedule I in the US, with protected religious use of peyote by the Native American Church.
How it's given in research: Single oral doses in healthy volunteers. Effects last roughly 6 to 14 hours depending on dose.
Strongest evidence: None for any condition above Very low. Almost no modern clinical trials.
Biggest open question: Whether it has any therapeutic advantage over shorter-acting psychedelics.

Evidence by condition

How strong the research is for each use, on our four-level evidence scale.

Depression, alcohol use and other conditions Very low

A 2026 systematic review found only 10 usable studies, of highly variable quality, reporting improvements in depression, alcohol and nicotine use and other symptoms. No modern randomised trials in patients.

What it is

Mescaline is the main psychoactive compound in the peyote cactus (Lophophora williamsii) and the San Pedro cactus. Both have been used in traditional medicine and ceremony for centuries.⁴ Peyote is a sacrament of the Native American Church, whose religious use is protected in US law.⁶

Chemically, mescaline is a phenethylamine, unlike psilocybin, LSD and DMT, which are tryptamines or related compounds.

How it works in the brain

Mescaline activates the serotonin 2A receptor, the shared target of classic psychedelics.² In healthy volunteers, it reaches peak blood levels about two hours after being swallowed, with a half-life of about 3.5 hours. Its effects last from about 6 hours at low doses to 14 hours at high doses.²

Key studies

Mescaline vs LSD vs psilocybin, 2023. In a double-blind crossover study in 32 healthy volunteers, 500 mg of mescaline produced subjective effects comparable to 100 µg of LSD and 20 mg of psilocybin.¹

Dose-response, 2024. In 16 healthy volunteers given doses from 100 to 800 mg, effects increased with dose. Doses above 100 mg raised blood pressure, and nausea and vomiting were frequent at the highest dose. Blocking the serotonin 2A receptor with another drug dampened and shortened mescaline’s effects, confirming that receptor’s central role.²

Religious peyote use, 2005. Researchers compared 61 Navajo Native American Church members who regularly used peyote in ceremonies with 79 people who used few substances. They found no psychological or cognitive deficits linked to peyote use.³

Therapeutic use, 2026 review. A systematic review found 66 relevant studies, but only 10 were suitable for analysis. They reported improvements in depression, wellbeing, and alcohol and nicotine use, but the authors concluded that the evidence is limited and too variable to draw firm conclusions.⁴

Safety and risks reported in research

Reported effects include nausea and vomiting (especially at high doses), headache, and rises in blood pressure and heart rate.²⁴ The long duration means experiences, including difficult ones, can last most of a day.

Legal and regulatory status

Canada: Mescaline is Schedule III under the Controlled Drugs and Substances Act, but the listing specifically excludes peyote.⁵
United States: Schedule I. The 1994 amendments to the American Indian Religious Freedom Act protect traditional peyote use for Indian religious purposes.⁶
Conservation: Peyote is considered vulnerable, and its conservation is a concern for Native American Church members and others.⁷

History in brief

Centuries ago: Peyote and San Pedro used in traditional medicine and ceremony.⁴
1994: US law protects religious peyote use by Native Americans.⁶
2005: Study finds no cognitive deficits among religious peyote users.³
2023–2024: First modern controlled studies of mescaline’s effects in healthy volunteers.¹²
2026: Systematic review finds the therapeutic evidence limited.⁴

Myths vs evidence

The claim“Mescaline is milder than LSD or psilocybin.”

What the evidence says False

In a head-to-head trial in healthy volunteers, a 500 mg dose of mescaline produced effects comparable to 100 µg of LSD and 20 mg of psilocybin.¹ Its effects also last longer, up to about 14 hours at high doses.²

The claim“Regular religious peyote use damages the mind.”

What the evidence says Unproven

A study of 61 Navajo members of the Native American Church who regularly used peyote in ceremonies found no psychological or cognitive deficits compared with people who used little or no substances.³ The authors caution that this may not apply to non-religious use.

See all myths vs evidence →

Frequently asked questions

What is the difference between mescaline and peyote?

Mescaline is the main psychoactive compound. Peyote is a small cactus, native to Texas and Mexico, that contains it. San Pedro is another cactus that contains mescaline.

Why is there so little clinical research on mescaline?

Its long duration makes sessions impractical. Researchers have also focused on psilocybin, LSD and shorter-acting compounds. Modern studies so far have mainly measured its effects in healthy volunteers.

Is peyote endangered?

Peyote is listed as Vulnerable by the IUCN. Its slow growth, habitat loss and harvesting pressure have raised concerns, including among members of the Native American Church, for whom it's a sacrament.

Is mescaline legal in Canada?

Mescaline is a Schedule III controlled substance, but Canada's law specifically excludes peyote from that listing. It isn't approved for any medical use. Talk to a qualified health professional about your own situation.

Clinical trials

No active trials in our tracker yet.

See all trials in the tracker →

References

Ley L, et al. Comparative acute effects of mescaline, lysergic acid diethylamide, and psilocybin in a randomized, double-blind, placebo-controlled cross-over study in healthy participants. Neuropsychopharmacology. 2023;48(11):1659–1667. Source
Klaiber A, et al. Acute dose-dependent effects of mescaline in a double-blind placebo-controlled study in healthy subjects. Translational Psychiatry. 2024;14(1):395. Source
Halpern JH, et al. Psychological and cognitive effects of long-term peyote use among Native Americans. Biological Psychiatry. 2005;58(8):624–631. Source
Shaw J, et al. The ethnopharmacological use of mescaline for psychiatric disorders: a systematic review. International Journal of Molecular Sciences. 2026;27(7):3081. Source
Government of Canada. Controlled Drugs and Substances Act (S.C. 1996, c. 19), Schedule III: "Mescaline ... but not peyote (lophophora)". Source
US Congress. American Indian Religious Freedom Act Amendments of 1994 (Public Law 103-344). Source
University of Idaho. The Peyote Path: a Newe perspective on conserving a sacred medicinal plant in peril (doctoral dissertation). Source