At Blue Morpho, we believe informed decisions start with reliable information. Research into plant medicine is expanding, but the evidence varies between substances. If you’re comparing ayahuasca and San Pedro retreats, understanding what current studies support and where evidence is still emerging can help guide your decision.
What the Clinical Trials Show About Ayahuasca and Depression
Ayahuasca has a stronger evidence base. A double-blind, randomized, placebo-controlled trial at a Brazilian university hospital tested ayahuasca in patients with treatment-resistant depression, people who hadn’t responded to at least two prior antidepressants. Those who received ayahuasca showed greater reductions in depression scores than the placebo group.
A Landmark Trial in Brazil
A 2026 Phase IIa trial from Imperial College London tested DMT, ayahuasca’s main psychoactive compound, in 34 people with depression. Those given DMT showed larger drops in depression severity than placebo, with effects lasting up to six months for some. A separate longitudinal study found similar patterns of sustained improvement over time (Frontiers in Psychiatry, 2026).
What Does the Evidence Say About San Pedro?
A 2026 systematic review screened 2,770 publications on mescaline, the primary psychoactive compound found in the San Pedro cactus, but found only 10 studies that met its inclusion criteria (MDPI, 2026). Those studies reported improvements in depression measures and substance use outcomes, although the overall body of evidence remains limited.
Why the Research Lags
Mescaline’s Schedule I status has limited formal study for decades. San Pedro has been used ceremonially for thousands of years, but longstanding traditional use is not the same as clinical evidence. Anyone considering an ayahuasca or San Pedro retreat should understand this difference in the available evidence before making a decision.
| Ayahuasca | San Pedro | |
| Study type | Randomized, placebo-controlled trials | Primarily observational and small studies |
| Studies of note | 2 major RCTs, 2026 Phase IIa trial | 10 studies met inclusion criteria from 2,770 publications screened |
| Reported findings | Reduced depression symptoms, with benefits lasting up to six months for some participants | Improvements in depression and substance use measures |
| Research stage | Growing clinical evidence | Early-stage research with limited clinical evidence |
Who Should Be Cautious
- Whether the facilitator screens for psychiatric history – not just physical health
- Whether any current medications could interact with ayahuasca or San Pedro
- Whether the retreat clearly explains the current evidence for each medicine
- Whether emergency medical protocols are in place
What the Research Can’t Fully Capture
Clinical trials happen in labs, not in a Maloca in the Amazon at night. In over 20 years of facilitating ceremonies in Iquitos, Peru, Maestro Hamilton Souther has observed patterns across thousands of participants that no single trial design captures: how setting, ritual, and multi-day integration shape a person’s experience alongside the medicine itself. That’s an observation, not a clinical claim. One thing we’ve learned directly: telling people upfront that San Pedro’s evidence is thin builds more trust than overstating what’s proven.
One Blue Morpho guest shared, “Hamilton is the real deal and has created a safe space in which to explore these sacred medicines… Aya is beyond explanation; if you’re called, let go of your fear and just go do it. Huachuma was very mellow, very “lovey”, and lasted most of the day.”
How to Evaluate a Retreat’s Claims
Whether you’re considering a luxury ayahuasca retreat or a simpler plant medicine retreat, ask which compound is being discussed, which condition is being studied, and what type of research supports the claim. A transparent retreat should explain both what current research supports and where evidence is still emerging.
Evidence and Experience, Read Together
Research on ayahuasca continues to grow, while research on San Pedro remains in an earlier stage. Science can explain part of the picture, while experienced facilitators provide practical context that clinical studies are not designed to measure. Together, they help people make more informed decisions.
If you’d like to learn more about Blue Morpho’s plant medicine retreats in Peru, including our approach to ceremony preparation, integration, and participant education, visit our website or email [email protected].
