Ayahuasca Research

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In the summer of 1993 a team of physicians and pharmacologists traveled into the Brazilian Amazon to examine, with diagnostic interviews and neuropsychological tests, the long-term members of a church that drinks a psychoactive tea as its sacrament. The tea was ayahuasca. The study that came of the visit, published by Charles Grob and colleagues in 1996 as the Hoasca Project, is where the modern research begins — a brew with centuries of ceremonial use in the Amazon, taken up by a clinical apparatus built to ask whether the things its drinkers report can be measured, and whether they hold up.

The substance has an unusual pharmacology, and the whole research program rests on a single fact about it. Ayahuasca characteristically combines two plants: one that supplies N,N-dimethyltryptamine, or DMT, a serotonergic compound that acts as an agonist at the 5-HT2A receptor — the same target that defines the classic psychedelics — and one that supplies β-carboline alkaloids of the harmala family, which inhibit the enzyme monoamine oxidase. DMT taken by mouth is ordinarily broken down before it can act; the monoamine-oxidase inhibition is what allows it to survive and reach the brain. That is the mechanism the literature returns to, and the source of the field’s most serious safety concern, addressed below. What matters here is that an orally active psychedelic exists at all, and that it arrived already embedded in a working tradition.

That embedding is the field’s first distinctive asset. Most psychedelics can be studied only in recreational populations or in volunteers dosed once in a lab. Ayahuasca is drunk regularly, across generations, by stable communities — the Brazilian syncretic churches União do Vegetal and Santo Daime, and indigenous Amazonian lineages such as the Shipibo — which makes available a long-term natural experiment no other compound offers. The Hoasca Project used it. Grob’s team compared fifteen long-term church members against fifteen matched controls who had never taken the tea and reported remission of prior psychopathology following the start of ceremonial use, no evidence of cognitive or personality deterioration, and high overall functioning among the users. The authors called it an unusual phenomenon worth further study, and were careful about what it was: a small, self-selected, non-randomized cohort, a striking observation rather than a causal demonstration. Larger work followed. José Carlos Bouso and colleagues in 2012 tracked 127 regular users against 115 controls drawn from non-ayahuasca religious communities, tested them at baseline and again a year later, and found the users scoring lower on every psychopathology measure, better on executive-function tasks, and higher on well-being — differences that largely held across the year, with, in the authors’ words, no evidence that ritual use “induce[s] the pattern of addiction-related problems that characterize drugs of abuse.” A 2018 survey of 1,947 church members across ten Brazilian states found alcohol- and tobacco-use disorders markedly below national norms, with attendance and years of membership tracking the reduction. These are associations in self-selected groups, not proof; what they establish is that decades of ceremonial use leave no visible wreckage, and something more like the opposite.

The clinical program proper grew out of those observations and arrived alongside the wider psychedelic revival. It is short and it escalates. In 2015 Flávia Osório and colleagues at the University of São Paulo gave a single dose to six volunteers in a current depressive episode and tracked them for three weeks, reporting fast reductions in depression scores with no induction of mania. In 2016 Rafael Sanches ran a larger open-label version, seventeen patients with recurrent depression, and added SPECT neuroimaging: depression scales fell from the first hours through day twenty-one, and blood perfusion rose in the left nucleus accumbens, right insula, and left subgenual area — regions tied to mood regulation. Neither trial had a control group, so neither could claim efficacy, and both said so; their function was to justify a real test. That test came in 2019, when Fernanda Palhano-Fontes and colleagues at the Federal University of Rio Grande do Norte, in Natal, published the first randomized, double-blind, placebo-controlled trial of ayahuasca for treatment-resistant depression. Twenty-nine inpatients received either ayahuasca or placebo in a single session. Depression scores were significantly lower in the ayahuasca group at days one and two, and sharply lower at day seven, where the effect size was large; the response rate at a week was sixty-four percent against twenty-seven on placebo, remission thirty-six against seven, the latter a trend short of significance. It is the strongest single result the field has, and it should be read for exactly what it is: one site, one dose, twenty-nine people, a seven- day horizon. The reviewers who praise it call, in the same breath, for larger and longer trials.

Those caveats are not incidental, and they belong to all of psychedelic medicine, not to ayahuasca alone. A trial like this is nearly impossible to blind — vomiting and the acute state announce themselves — so participants and staff can usually tell who received the drug, and the volunteers are a hopeful, self-selected population in whom expectancy alone can move a depression scale. The same problems that a 2024 reckoning found inflating the psilocybin literature apply here with extra force, on a far smaller evidence base. Beyond depression the picture is thinner still: observational studies report reduced grief in the bereaved and a non-randomized 2025 trial of ayahuasca-assisted grief therapy favored the active arm, and reviews place the brew among psychedelics that look promising for alcohol and tobacco dependence, especially alongside psychotherapy — but there is no dedicated anxiety-disorder trial and no confirmatory controlled trial for addiction in this material. Promising and preliminary are the honest words, with the weight on the second.

The neuroscience gives the clinical signal a mechanism to chase, and here the work converges with the psilocybin field. In 2015 Palhano-Fontes used fMRI to watch ten experienced subjects during the acute state and found activity falling across most of the default mode network — the system of self-referential, mind- wandering activity whose hubs are the posterior cingulate cortex and medial prefrontal cortex — with connectivity within the posterior cingulate loosening. A 2023 systematic review found this acute disruption of default-mode connectivity consistent across psychedelics, while cautioning that “it is unclear how central the DMN is to the therapeutic potential.” A 2017 study of the post- acute “afterglow” added a chemical layer: reductions in glutamate and related metabolites in the posterior cingulate that correlated with gains in non-judging mindfulness and predicted mindfulness two months on, implicating glutamatergic transmission in whatever lasts. And in cell cultures and mice, the β-carbolines and DMT itself have been found to stimulate the birth of new neurons and to modulate plasticity — a candidate substrate for an antidepressant effect, and a finding that lives entirely in the dish and the rodent, with no demonstration in human beings. These results have a tempting interpretation. The entropic-brain hypothesis holds that the richness of a conscious state indexes the disorder of spontaneous brain activity, and that psychedelics raise that disorder while the tightly organized default network comes apart — the very disorganization the ayahuasca scans show. It is an elegant bridge from the brew to a general theory of consciousness, and it is a theory: influential, contested, not the same kind of thing as a trial result. What can be said plainly is that a tea from the forest reliably quiets the brain’s center of self-narration, and that the quieting seems to matter to what follows.

The safety record, as the studies report it, is specific. Vomiting is a characteristic acute feature — in Sanches’s trial the only adverse effect, in nearly half the volunteers — and under controlled conditions the brew is generally described as well tolerated, with reviewers stressing patient screening and cardiovascular caution. The genuine hazard is pharmacological, and follows from the mechanism. Because the brew’s β-carbolines inhibit monoamine oxidase, combining ayahuasca with serotonergic medications — the SSRIs and SNRIs that depressed patients are most likely to be taking — risks dangerous excess of serotonergic activity, up to serotonin syndrome; modeling work and toxicology case reports, the latter centered on polydrug deaths involving other serotonergic compounds, sharpen the warning. This is documented finding, not counsel, and the distinction is the point: the pharmacology is established, the therapeutic promise is not, and the interaction risk is exactly what a research program exists to map before anyone relies on it.

It is also one of the few psychedelics whose study was made possible by a courtroom. In 2006 the United States Supreme Court ruled unanimously, in Gonzales v. O Centro Espírita Beneficente União do Vegetal, that the Religious Freedom Restoration Act protected the UDV’s sacramental use of the DMT-containing tea against federal prohibition; the government had not shown the compelling interest strict scrutiny demands. A 2009 federal decision extended the same protection to Santo Daime. Those rulings are why legally recognized ceremonial communities persist on American soil, and they are the practical ground beneath cohort research everywhere — the churches are not subjects to be extracted from but partners in the work. Around them an institutional ecosystem has formed: Brazilian universities at its center, Natal and São Paulo and Campinas, alongside ICEERS and the Beckley Foundation, whose multi-year observational study at a Peruvian center enrolled hundreds. The science studies a tradition it did not create and does not pretend to own. The indigenous Amazonian origin is the context, named with respect and described no further; the subject is what happens when the instruments of the clinic are turned on something the forest has been doing for a very long time.

What this suggests — and the connection is interpretive, not established — is that ayahuasca research keeps measuring, in its own vocabulary, a through-line the older material would recognize. Across the observational studies the perceived mystical or ego-dissolving quality of the experience repeatedly mediates the outcome: the change tracks not the dose but the depth of what happened. The default network goes quiet, the sense of a bounded self loosens, and people come back reporting more well-being, less fear, a different relation to their grief. The brew came to the laboratory carrying a claim its communities never needed an instrument to make — that drinking it, in the right setting, can heal and reorient a life. The trials are too small to confirm that claim and too suggestive to dismiss it. What the research has produced so far is narrower than either hope or dismissal would prefer: a few small trials, a handful of long-running cohorts, and a signal strong enough to be worth the careful, unfinished work of testing it.

→ Related: Psilocybin Research · Near Death Experience · Brazilian Syncretic Religions Santo Daime Udv Barquinha · Placebo Effect · Collective Unconscious