Review of 18 long-term studies on ayahuasca and mental and physical health

The question

What do long-term follow-up studies show about the mental and physical health effects of ayahuasca, a psychedelic plant brew traditionally used in Central and South America?

What they did

The authors searched for prospective studies, meaning studies that measured people before ayahuasca use and followed them forward in time, and that reported longer-term health outcomes. Eighteen studies met their criteria. Most of these studies recruited unselected volunteers who were already attending ayahuasca retreat centres. The authors then described the patterns of results across studies rather than pooling them into a single statistic.

What they found

Across the studies, longer-term changes were reported in wellbeing and quality of life, depression and other psychiatric symptoms, substance misuse, cognitive flexibility (the ability to switch between ways of thinking), personality and prosocial behaviour. Improvements in mental health tended to show up at the group level. However, some studies also identified subsets of participants who had lasting psychiatric problems linked to their ayahuasca use. No study focused specifically on physical health conditions, though one reported a drop in physical pain symptoms and another reported lasting changes in brain chemistry in a region called the posterior cingulate cortex.

The fine print

The authors themselves note that many included studies had small samples, no control or comparison group, non-random designs, and doses that were not standardized, so improvements cannot be attributed to ayahuasca itself. Most participants were self-selected people travelling to retreats, who may expect and report benefit. The review describes findings narratively rather than combining them statistically, and no total number of participants is given. This summary is based on the abstract only.

What it means

Follow-up studies of ayahuasca retreats generally report improvements in wellbeing and psychiatric symptoms, but the research is too weakly designed to show that ayahuasca caused those changes, and a minority of people reported lasting psychiatric problems.

Evidence grade: Low. A systematic review, but the studies it pooled were mostly small, uncontrolled and non-randomized observational studies of people who chose to attend retreats.

This summary is based on the study’s published abstract.