A new study led by ICEERS researchers documents significant and lasting psychological changes in Western participants who attended ayahuasca retreats run by Shipibo healers in the Peruvian Amazon. The research, published in the journal Psychedelics, constitutes the most comprehensive personality analysis conducted to date with this dataset, and falls within the paradigm of Symmetrical Global Mental Health: a framework that proposes a reciprocal and non-extractive relationship between Indigenous and Western medical systems.
The dataset comes from the Temple of the Way of Light, a retreat center in the Peruvian Amazon that works with Shipibo healers, and has served as the basis for previous ICEERS research: an analysis of fifty participants focused on grief (González et al., 2020) and a well-being study involving two hundred participants (González et al., 2021). Both found sustained improvements in quality of life and decentring at three, six, and twelve months following the retreat. The research now being published expands on that foundation with the full sample of 264 participants and incorporates, for the first time, a comprehensive personality assessment using the NEO-FFI.
Profile of the participants
The sample presents a homogeneous profile: a median age of 41, an equal distribution by gender, a high level of education (85% with a college degree), and the majority from the United States, Canada, the United Kingdom, and Australia. One piece of data stands out as relevant for interpreting the results: 33.7% reported suffering from anxiety, 27.3% from depression, 12.5% from grief, and 6.1% from post-traumatic stress at the start of the retreat. However, only 45% had received a prior formal diagnosis.
The main motivations for attending the retreat were spiritual growth (47%), personal development (28%), and therapeutic seeking (22%). No participant identified recreational use or escapism as a primary motivation, confirming a pattern already documented in previous ICEERS studies with ritual ayahuasca users: they do not score high on sensation seeking, contrary to what characterizes problematic substance use.
What the data show
Twelve months after retirement, the results indicate significant changes in three of the five personality traits assessed. The most striking change concerns neuroticism, a trait that measures the tendency to experience negative emotions such as anxiety, sadness, or irritability. One year after retirement, the percentage of participants with high levels of neuroticism had fallen from 39.8% to 28.6%, while those with low levels had increased from 23.9% to 39.0%. In practical terms: four out of ten participants who arrived with a high negative emotional burden had reduced that tendency in a measurable and sustained way. Extraversion also increased, albeit more moderately.
Quality of life improved across all assessed domains: psychological health, social relationships, physical health, and perception of the environment. The effects were particularly pronounced in the psychological dimension and in social relationships, suggesting that the changes were not limited to the individual’s inner world but also extended to their daily life and connections. The most notable change in the entire study, however, occurred in the capacity for defusion: the ability to observe one’s own thoughts and emotions as events passing through the mind, without becoming caught up in them. It represents, in a way, the opposite of rumination: instead of merging with the distress, the person learns to view it from a certain distance.
91.7% of participants reported experiencing long-term benefits, primarily in spiritual well-being (80.3%), personal well-being (76.1%), and mental health (71.6%). Adverse effects were minimal: only 2.3% of participants reported any harm or lasting negative effects.
Regarding substance use, the study recorded a finding that warrants context: the frequency of use in the past month increased slightly across the entire sample, but when broken down by substance, the increase was limited exclusively to tobacco. For alcohol, cannabis, cocaine, amphetamines, and other psychedelics, the proportion of participants who reported not having used these substances increased in a statistically significant manner. This pattern is consistent with the existing literature on the effects of ayahuasca on problematic substance use.
The role of Shipibo healers
One of the most significant findings from a public health perspective concerns what the participants themselves considered to be the most decisive factor in their process. When asked what factor had been most important during the retreat, 41.6% cited their experiences with ayahuasca, but 26.6% attributed the greatest importance to the work of the Shipibo healers, and 15.9% to a combination of factors. Only 0.9% highlighted complementary therapies such as yoga or meditation.
This result, consistent with the literature on Amazonian medicine that describes the therapeutic process as fundamentally relational, has direct implications for the debate on the medicalization of psychedelics: if non-pharmacological factors — in particular the relationship with the healer, the singing of the icaros, and the ritual structure — play a central role in the outcomes, removing the molecule from its ceremonial context to administer it in a clinical setting means losing a substantial part of what makes the medical system as a whole effective.
The correlation analysis reveals a finding with direct implications for harm reduction. Participants who arrived at the retreat with greater psychological distress also exhibited lower capacity for decentring at baseline, as well as higher neuroticism. Given that decentring acts as a resilience factor against emotional suffering — by reducing identification with disturbing thoughts and emotions — the authors suggest that strengthening this capacity, especially in people with greater emotional instability, could serve as a protective factor both in ceremonial contexts and in more structured therapeutic interventions.
Symmetrical Global Mental Health as a framework
The study does more than just provide data: it takes an explicit stance on how research in this field should be conducted. The Sym-GMH paradigm argues that the global mental health crisis cannot be addressed solely by exporting psychiatric systems from the Global North to the Global South, nor by extracting traditional knowledge to repackage it in Western clinical formats. The alternative lies in a genuine dialogue between therapeutic paradigms, one that preserves the cultural integrity of practices, recognizes the epistemic agency of the communities that uphold them, and articulates health policies capable of accommodating diverse modalities of healing.
The authors themselves acknowledge the tensions inherent in this approach: Indigenous responses to growing Western interest are not uniform, and the risks of cultural appropriation, economic imbalances, and neocolonial dynamics constitute real risks that any framework claiming to be non-extractive must address honestly. The Sym-GMH does not resolve these tensions, but incorporates them as a constitutive part of the problem.
For ICEERS, which has spent nearly two decades generating knowledge about ayahuasca from an approach that does not separate the scientific dimension from the cultural and ethical dimensions, this study represents a logical continuation of that trajectory. The full article, available open access, can be found here.