The word "psychedelic", from the Greek for "mind-revealing", covers a small family of compounds that temporarily change perception, mood, and thought. Most of them are natural: they come from mushrooms, cacti, tree bark, and vines that people have used in ceremony for thousands of years. Two of the best known, LSD and MDMA, are the family's only true synthetics. This page introduces each one honestly: what it is, what it does, and what the evidence shows. Metanoia's focus is the natural psychedelics, but understanding the whole family is where any clear thinking about them has to begin.
One key that fits many locks
Almost all the classic psychedelics work through a single doorway in the brain: a serotonin docking site called the 5-HT2A receptor. These molecules resemble serotonin closely enough to switch that receptor on, which loosens the brain's habitual, top-down control of perception and lets normally-filtered signals rise to the surface. (MDMA is the exception: it works mainly by flooding the brain with serotonin rather than mimicking it, which is why it belongs slightly apart from the rest.)
Beneath that shared doorway sits something deeper and, for a book about growth, more important: neuroplasticity, the brain's capacity to form new connections and reorganize itself. It is the thread that ties the whole family together. Psilocybin grows new dendritic spines from inside the neuron (Vargas & Olson, 2023). Ayahuasca's harmine raises BDNF, a key growth protein, and spurs new neurons. In rats, iboga's ibogaine raised GDNF protein in one dopamine-related brain region and raised BDNF gene expression in several regions, although BDNF protein itself did not rise significantly (Marton et al., 2019). Three separate traditions, on three continents, each independently found a molecule that opens the brain's window of change. That is the unifying principle of everything below.
The natural psychedelics
Psilocybin mushrooms
Natural · Our focusThe "magic mushrooms", over 100 species of Psilocybe, used as sacraments in Mesoamerica for millennia and called teonanácatl, "flesh of the gods." Psilocybin is a prodrug: your body converts it to active psilocin, which reaches the 5-HT2A receptor. The mushroom is not one molecule but a whole chemical system, the subject of our first book. For depression, a 2025 systematic review and meta-analysis of nine randomised trials with 602 participants found psilocybin moderately superior to control (Borgogna et al., Psychopharmacology). The same review reported a high risk of bias in most of the trials, smaller effects in the larger and better-controlled trials, financial conflicts of interest in almost all of the studies, and no group comparison beyond three months. The signal is real, and the evidence base is still young.
DMT & Ayahuasca
NaturalDMT is a short, intense tryptamine found throughout nature and in trace amounts in the human body. Swallowed alone it does nothing: an enzyme in the gut (MAO) destroys it first. The peoples of the Amazon solved this without any chemistry: ayahuasca combines a DMT-containing plant (chacruna) with the Banisteriopsis caapi vine, whose beta-carbolines block that enzyme, letting the DMT reach the brain. It is one of the most sophisticated pharmacological discoveries in human history, one the West only understood in the 1980s. Brazil legalized ceremonial use in 1987. A placebo-controlled trial (Palhano-Fontes) showed a rapid antidepressant effect in treatment-resistant depression.
The DMT volume and the ayahuasca volume, both in preparation
Mescaline: peyote and San Pedro
NaturalOne of the oldest psychedelics known, mescaline comes from cacti: the slow-growing peyote of Mexico and Texas, and the fast-growing San Pedro (wachuma) of the Andes. Unlike the others it is a phenethylamine, but it still acts on the 5-HT2A receptor, with a long, gentle arc. Peyote is also the family's clearest ethical lesson: it is listed as vulnerable, protected for the Native American Church, and Indigenous leaders have asked that it be left alone, which is exactly why Metanoia favors sustainable, cultivable sources like San Pedro and mushrooms over threatened wild ones.
5-MeO-DMT: the "God molecule"
NaturalA powerful, short-acting tryptamine found in certain plants and famously in the venom of the Sonoran Desert toad. It produces ego-dissolution and a sense of unity, often with a bright white light and, unusually, few visuals. Observational studies report rapid, lasting improvements in well-being. It also carries an important honest footnote: the toad is the only vertebrate that makes it, demand threatens the animal, and the popular "ancient Indigenous use" story is largely invented. Here, unlike the mushroom, the pure synthetic version is arguably better, as effective, far safer, and it spares the toad. Whole-versus-isolated must be argued organism by organism, never as a slogan.
Iboga & ibogaine
NaturalFrom the root bark of the Tabernanthe iboga shrub of Gabon, at the heart of the Bwiti spiritual tradition. Its alkaloid ibogaine is unlike the others, a long, dreamlike, deeply introspective state (an "oneirogen") rather than a classic visionary trip, and a striking record for interrupting opioid addiction. A 2024 Nature Medicine study of special-forces veterans with traumatic brain injury (MISTIC) found improvements in PTSD, depression, and functioning, using magnesium to protect the heart. That cardiac risk is real and serious, which is why iboga is strictly a clinical, supervised matter, never a casual one.
The two classic synthetics
LSD
SyntheticAlbert Hofmann synthesized LSD in 1938 and discovered its effects in 1943, the molecule that opened the modern chapter of this whole story. It is extraordinarily potent (active in micrograms) and long-lasting. In June 2026 the company Definium announced topline results from Emerge, a placebo-controlled Phase 3 trial of DT120, a pharmaceutical form of LSD, in 149 adults with major depressive disorder. The company reported a placebo-adjusted improvement of 8.1 points on the MADRS depression scale at week 6. The trial had no active comparator, so it did not test DT120 against any approved antidepressant. These are topline results announced by the company, not a peer-reviewed paper.
MDMA
SyntheticNot a classic psychedelic but the family's close cousin, an "empathogen" that works by releasing serotonin, producing warmth, openness, and reduced fear rather than visions. Its most studied use is for PTSD, where it has been through late-stage trials (including MAPS-sponsored work). It occupies a distinct place: less about perception, more about emotional safety and connection.
Where the science stands in 2026
This is a genuine turning point. After decades in the wilderness, psychedelic medicines are moving through the final stages of drug approval, and a real race is underway:
- Compass Pathways: synthetic psilocybin for treatment-resistant depression. Two positive Phase 3 trials, an FDA priority review, and a rolling submission underway.
- Usona Institute, psilocybin for major depression (a broader population), also with a priority voucher.
- Definium, pharmaceutical LSD for depression, with company-reported topline results from a placebo-controlled Phase 3 trial in June 2026.
- Transcend, a selective MDMA-analog for PTSD that skips the "trip."
- In April 2026 Executive Order 14401 directed federal agencies to speed the review of psychedelic drugs for serious mental illness. It did not change any drug's legal schedule.
Note: these remain investigational and, legally, Schedule I. Nothing here is medical advice.
Want the whole story of one of these, told in full? Start with our free book on the mushroom, and watch this library grow.