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Mental Health Benefits of Ayahuasca Ceremonies May Be Due to a Placebo Effect, Study Finds

By Alexander Beadle

Published: Dec 20, 2021   

Image credit: Jared Rice via Unsplash

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Participants in ayahuasca ceremonies report reductions in stress, anxiety, and depression whether they are given ayahuasca or not, a placebo-controlled study from researchers at Maastricht University has found.

Published in the journal Psychopharmacology earlier this year, the research details results from six different European ayahuasca retreats where trainee retreat facilitators were given either ayahuasca or a placebo during the session. The outcomes were seen to be very similar between both the ayahuasca and placebo groups, though the group that received ayahuasca uniquely demonstrated increased empathy.

The researchers say that these observations speak to the importance of conducting more placebo-controlled experiments with psychedelics.

Ayahuasca and mental health

Ayahuasca is a hallucinogenic brew made from the leaves from the Psychotria viridis bush and cuttings from the Banisteriopsis caapi vine. This brew has been used traditionally by many different indigenous groups from the Amazon basin for centuries, usually as a part of spiritual and cultural ceremonies led by an experienced shaman or curandero.

Ayahuasca ceremonies are still an important part of many Amazonian cultures today, though the past few decades have seen a rise in “ayahuasca tourism” from Westerners in South America and an increasing number of ayahuasca retreats put on in Western countries. These retreats generally tend to be less of a cultural practice and instead focus predominantly on the altered states of consciousness that come with ayahuasca use.

The growing prevalence of ayahuasca use worldwide, plus anecdotal tales of its beneficial effects on mental health, has also sparked scientific interest in the drug. Early research has shown that ayahuasca demonstrates promise as a rapid antidepressant and as a way to address traumatic memories. However, there is a general lack of placebo-controlled studies that have examined the drug to date.

In the observational study, the Maastricht University researchers sought to identify any changes in the mental health of experienced ayahuasca users when given ayahuasca or placebo during a retreat. They also tested the effect of set and setting. In psychedelics research, set is generally defined as being the intentions, mood, and expectations of the individual taking the psychedelic, while setting refers to the wider context in which the drug use takes place, such as the social group environment and sensory stimulation of an ayahuasca retreat.

Ayahuasca ceremonies reduce stress and depression, even when a placebo is used

The study looked at six ayahuasca retreats held in Europe. The study participants were all described as being “students of an ayahuasca school” who were training to become ayahuasca retreat facilitators and so were reasonably experienced with ayahuasca. The retreat staff randomly assigned these students to receive either ayahuasca or a placebo substance made by the retreat staff. The participants were not told which they had received.

Before and after the retreat session, all participants underwent a battery of assessments to determine their levels of stress, mindfulness, and empathy, as well as to identify any existing symptoms of depression or anxiety. The morning after the session, participants were asked to evaluate their psychedelic experience using questionnaires aimed at assessing ego dissolution and altered states of consciousness.

The researchers found that both the placebo and ayahuasca groups reported similar decreases in anxiety, depression, and stress levels after the retreat session. Those in the placebo group tended to report slightly stronger reductions in depression symptoms, where the ayahuasca group demonstrated increased emotional empathy on the Multifaceted Empathy Test (MET).

“This suggests an important role for non-pharmacological factors, such as set and setting,” the researchers wrote.

Since the students each had multiple past experiences with ayahuasca, it is possible that their expectations for or learned associations with ayahuasca ceremonies could explain the decreases in stress and anxiety reported under placebo.

“In the context of the present study, one might speculate that (repeated) suggestion of the positive mental health effects of ayahuasca, by either peers or facilitator(s) throughout the ceremony, may have contributed to the positive changes in mental health parameters that were observed after the ceremony in both groups,” the researchers wrote.

Low-dose psychedelics and the placebo effect

The study authors noted several limitations of the study. Firstly, since it was observational and the ayahuasca and placebo drugs were both provided by the retreat staff, the researchers were not able to control the administration of the drugs or their potency.

Overall mean subjective ratings of the psychedelic experience (such as ego dissolution) were noted to have been low in both the ayahuasca and placebo groups, indicating that the doses of psychedelic used were likely much lower than would be administered in a clinical setting. The researchers suggest that this could explain why, with the exception of empathy, both groups reported similar results after the retreat session.

Alternatively, they suggest a possibility where the users in the ayahuasca group may have reported lower effects, as they dampened their expectations under the awareness that they could be given a placebo, while those in the placebo group heighted their reports, as they were affected by the set and setting of the ayahuasca retreat.

Previous research into microdosing has found that the positive effects on mental wellbeing reported after using low doses of psychedelics can largely be explained by the placebo effect. However, the researchers behind this study believe that more work still needs to be done to fully evaluate the pharmacological effects of ayahuasca and the non-pharmacological effects of set and setting on mental health.

“The present findings do not mean that change in mental health outcomes following ayahuasca administration is always based on expectation and should always be qualified as a placebo effect,” the researchers argued in their paper.

“In sum, the current findings demonstrate that improvements in mental health of participants in naturalistic ayahuasca ceremonies can be driven by non-pharmacological factors that elicit a placebo response but also by pharmacological factors that are related to the use of ayahuasca.”

They suggest that further research should look at the effects of ayahuasca on novice users, rather than trainee retreat facilitators, as they might be more susceptible to the drug’s pharmacological impacts. Additionally, examining different doses of ayahuasca, as well as other psychedelics given in a ceremonial group setting, could also help to characterize the drug’s effect and the effect of set and setting on mental health following psychedelics use.


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