Adverse Effects of Ayahuasca: Results from the Global Ayahuasca Survey

About this resource

This is an English version of a paper analyzing physically and psychologically difficult or potentially adverse effects in a large international online survey of people with ayahuasca experience. The survey was conducted from 2017 to 2019 and included 10,836 participants from more than 50 countries. Analyses of physical effects used responses from 8,216 people, while analyses of mental effects used responses from 7,839.

This was not a clinical trial that prospectively collected medical records; it was a cross-sectional survey in which respondents recalled past experiences. It can capture broad real-world experience, but it cannot determine whether reported events were caused by ayahuasca or whether their frequency is the same among all users. Interpretation also requires care when deciding how to count vomiting and similar events, which may be culturally understood as “purging,” as adverse physical reactions in a survey.

Study design

Participants answered online questions about their history of use, type of setting, health status, acute physical reactions, mental and emotional changes after use, and whether they sought medical or professional support. Researchers statistically explored associations between the presence of reactions and factors such as age, physical and mental health, frequency of use, and context.

Recruitment through websites, social media, related organizations, and other channels was not random sampling. People with a strong interest in use and people motivated to report either positive or negative experiences may have been more likely to participate. The botanical identity, constituent concentrations, contaminants, and concomitant medications in respondents’ brews were not verified in a laboratory.

Content

The survey asked about vomiting, nausea, headache, abdominal pain, difficulty breathing, chest pain, fainting, seizures, and other acute physical reactions. It also addressed whether anxiety, low mood, fear, disconnection, visual or auditory difficulties, and related experiences persisted afterward, how long they lasted, and how they affected daily life.

Cultural meaning and medical classification need to be separated here. Vomiting and intense emotional experiences are understood as positive processes in some traditions and by some participants. Finding personal meaning, however, is not the same as showing that clinical risks such as dehydration, aspiration, electrolyte abnormalities, or psychological crisis are absent. The study itself places side by side the fact that many difficult reactions were evaluated as part of a positive experience and the proportion of respondents who needed support.

Results

At least 1 acute physical reaction was reported by 69.9% of respondents. Most involved vomiting or nausea, and 2.3% reported seeking some form of medical attention. These percentages do not uniformly represent symptom severity or causation; they are self-reported frequencies of events experienced by respondents.

Mental difficulties after use were reported by 55.4%. Most were described as temporary, but approximately 12% of respondents sought professional support. Among those reporting difficulties, 87.6% regarded the experience as part of a positive process of growth or integration. The result is therefore twofold: subjective positive evaluation was high, yet events requiring support cannot be disregarded.

Poorer health, a history of mental illness, conditions of supervision or support, and certain other factors were associated with difficult reactions. These are associations, not a diagnostic model that precisely predicts an individual’s probability of an event. Associations between more frequent use and fewer reports of some reactions may have several explanations, including tolerance, selection of experienced users, or different reporting thresholds; they do not show a causal safety effect.

Limitations

Major limitations include a self-selected online sample, recall error, cultural and linguistic differences, and broad definitions. People who experienced serious adverse events may have been more likely to respond, while people favorable toward ayahuasca communities may also have been overrepresented. Those with more episodes of use may have greater difficulty counting individual past events accurately.

The composition and amount of brews were not verified, and concomitant medications, other substances, prior conditions, and environmental factors cannot be separated completely. Associations in a cross-sectional survey do not establish causation, and there was no comparison with people without experience or with another intervention. This survey alone cannot estimate the incidence of death or extremely rare events.

The number of respondents varied by question, and not all 10,836 people were included in every analysis. Meanings of “adverse,” “difficult,” “necessary purging,” and “professional support” may differ by country and ritual culture. Whether translated questionnaires measured the same concepts equivalently is another uncertainty when comparing percentages.

Safety

The presence of respondents who sought medical or professional support in this large survey shows that risk does not disappear merely because a substance is “natural,” “traditional,” or positively evaluated by many people. Dehydration or aspiration associated with vomiting, acute cardiovascular changes, psychological confusion, pre-existing disease, drug interactions, and conditions of supervision need to be evaluated separately.

This page provides no instructions for self-use. Strong anxiety, confusion, altered consciousness, chest pain, seizures, and persistent mental symptoms should not have medical assessment delayed solely because of cultural interpretation. Survey findings also cannot serve as a screening method that guarantees an individual’s safety.

The group-level proportion stating that an experience was ultimately positive does not cancel out those who needed support during it or the minority whose difficulties continued over the long term. Separating an average evaluation from an individual’s severity is central when using this survey as a safety resource.

People unable to answer an online survey, as well as deaths, are not captured by the same method. Aggregate percentages should not be used alone to infer the worst outcomes; they need to be read alongside other evidence such as case reports and toxicity reviews.

That is the appropriate place of this survey within the evidence.

Source and rights

Original source: Bouso JC, et al. Adverse effects of ayahuasca: Results from the Global Ayahuasca Survey. PLOS Global Public Health. 2022;2(11):e0000438. DOI: 10.1371/journal.pgph.0000438.

The original article is available under Creative Commons Attribution 4.0 (CC BY 4.0). This page is a source-aligned English translation under that license, with the survey design and limitations reorganized into a more readable sequence. Tables and figures from the original are not reproduced.