Amazonian traditions

How anyone discovered that two specific plants combine to make an orally active drug is a genuine unsolved question — and the tourism built on the answer has killed people.

What it is

The religious and healing traditions of the peoples of the Amazon basin — Shipibo-Conibo, Asháninka, Shuar, Huni Kuin, Yawanawá, Tukano, and a great many others across Peru, Brazil, Ecuador, Colombia and Bolivia.

They are not one tradition and the differences are substantial. What they are known for outside the region is ayahuasca, and the attention has been mixed in its effects.

Where it came from

Traditions of indeterminate antiquity, documented from the colonial period onward and disrupted severely by it — by disease, by the rubber boom's atrocities, by mission activity, and by continuing pressure on land.

Ayahuasca poses a genuine puzzle. The brew combines two plants: Banisteriopsis caapi, the vine, which contains harmine and related monoamine oxidase inhibitors; and typically Psychotria viridis, whose leaves contain DMT.

Neither works well alone by mouth. DMT taken orally is destroyed in the gut by monoamine oxidase before it reaches the brain. The MAOIs in the vine prevent that, making the DMT orally active.

The Amazon contains something on the order of eighty thousand plant species. Two of them, prepared together by prolonged boiling, produce an effect that neither produces separately, through a pharmacological mechanism identified by Western science only in the twentieth century.

How this was arrived at is not known. The communities' own accounts generally say the plants told them. Researchers have proposed trial and error over a very long period, or the systematic exploration of bitter plants, and neither explanation is satisfying given the numbers. It remains an open question, and it is a more interesting one than most of the claims made about the brew.

Syncretic churches emerged in twentieth-century Brazil — Santo Daime (from the 1930s) and União do Vegetal (1961) — combining ayahuasca with Christian and spiritist elements. They are legally recognised in Brazil, and in 2006 the United States Supreme Court ruled unanimously in Gonzales v. O Centro Espírita that the UDV could use the brew in worship.

How it is practised

This article does not describe ceremony. Publicly known features: sessions held at night, led by a practitioner, over several hours; icaros, the songs that structure a Shipibo ceremony and are regarded as the practitioner's working instruments; and dieta, extended periods of isolation and dietary restriction under a particular plant, which is the training rather than the ceremony.

What we can and cannot say

We can say the research is real and early. A small randomised controlled trial by Palhano-Fontes and colleagues (2019) found rapid antidepressant effects in treatment-resistant depression, and observational work suggests possible benefit in addiction. These are preliminary findings with small samples, and the broader psychedelic research programme they sit within is discussed under medical harm.

And we have to be direct about the harms, because the tourism is large and the marketing is not.

Drug interactions can kill. MAOIs interact dangerously with a long list of substances. Taking ayahuasca while on SSRIs or other serotonergic antidepressants risks serotonin syndrome, which can be fatal. Interactions with stimulants, certain opioids, some cold remedies and tyramine-rich foods are also documented. Many retreat operators ask about medications; some do not; and people have died.

Pre-existing conditions matter. Personal or family history of psychosis or bipolar disorder is a serious contraindication. Cardiovascular problems are a risk given the strong physiological effects.

Deaths have occurred at retreats — from interactions, from underlying conditions, and from accidents and violence while participants were incapacitated.

And sexual assault by practitioners is documented and not rare. Multiple credible accounts and investigations describe assaults on women during or after ceremonies, in a setting combining profound vulnerability, a practitioner with unquestionable authority, and no institutional accountability whatsoever. It is exactly the structure described under the guru problem, with the additional factor that the victim's account can be dismissed as a product of the medicine.

We can say the communities are ambivalent and are not consulted enough. The tourism brings income to some of the poorest regions in South America, and it also brings unqualified operators claiming credentials nobody granted, pressure on plant populations, distortion of local practice toward what visitors will pay for, and a market in which "shaman" is a job title anyone can adopt. Indigenous federations have issued statements about it. They are not much read.

We cannot teach anything here, and would not. Icaros belong to the people who sing them.