In brief
- A double-blind, placebo-controlled trial evaluated a single dose of ayahuasca in 29 individuals with treatment-resistant depression.
- Seven days later, 57% of the ayahuasca group responded to treatment, compared to 20% in the placebo group.
- While these results are promising, the sample size was small, the trial occurred in a supportive hospital setting, and it does not justify self-treatment.
The idea that an Amazonian brew used in ritual contexts could relieve depression unresponsive to standard medication sounds, at first glance, like an overblown claim. In 2019, however, a Brazilian research team published the first randomized, placebo-controlled clinical trial investigating ayahuasca for treatment-resistant depression. The results were fast-acting and encouraging, though they demand a level-headed appraisal: this was a small, preliminary trial, not definitive proof.
The Study
Authored by Fernanda Palhano-Fontes and colleagues, the paper was published in Psychological Medicine (Cambridge University Press) in 2019. It was a parallel-arm, randomized, double-blind, placebo-controlled trial conducted at a university hospital in Natal, Brazil. Twenty-nine participants diagnosed with treatment-resistant depression—meaning they had not improved after trying at least two conventional antidepressants—took part. They were randomly assigned to receive either a single dose of ayahuasca (14 participants) or a placebo (15 participants). The placebo was carefully formulated to mimic the brew’s bitter taste and brownish color, making it difficult to distinguish. Both groups received their dose in a quiet room, supported and supervised by clinical staff. Depression severity was assessed using standardized clinical scales (HAM-D and MADRS) before the session and at one, two, and seven days post-administration.
The Findings
The difference between the two groups was statistically significant at every evaluation point and widened over time. On the primary scale (HAM-D), the between-group comparison at seven days yielded a large effect size (Cohen’s d = 0.98). On the MADRS scale, the effect grew from moderate on day one (d = 0.84) to large by day seven (d = 1.49). In terms of response rates—defined as at least a 50% reduction in depressive symptoms—57% of those who received ayahuasca met criteria at seven days compared to 20% in the placebo group on the HAM-D, and 64% versus 27% on the MADRS. Remission rates (near-complete absence of symptoms) reached 43% versus 13%, though this difference hovered at the edge of statistical significance (suggesting a trend rather than a certainty). Notably, the placebo group also showed measurable improvement—a standard occurrence in depression research that underscores the essential role of a control group.
What This Means (and What It Doesn’t)
The trial’s findings are notable for two main reasons. First, the therapeutic response was rapid: clear differences compared to placebo emerged just one day after administration, whereas standard antidepressants typically take weeks to exert meaningful effects. Second, the cohort consisted of patients whose depression had proved intractable to existing pharmacological options—a population notoriously difficult to treat. Even so, the study’s limitations must be acknowledged plainly. The sample was very small—just 29 people—which requires cautious interpretation and demands larger trials before firm conclusions can be drawn. Follow-up lasted only one week, leaving long-term durability unanswered. Furthermore, the authors noted an inherent challenge in psychedelic research: maintaining the blind is difficult because participants often realize whether they received an active substance, a factor that can influence subjective symptom ratings.
The clinical framework behind these outcomes is equally critical to understand. The dose was administered in a medical environment with preparatory sessions, continuous personal support during the acute experience, and medical supervision prepared to manage adverse reactions. This bears little resemblance to unguided personal use. Ayahuasca is not benign: it frequently induces vomiting, physical distress, and intense psychological anxiety, and it poses severe, potentially life-threatening interactions with certain medications and medical conditions. A positive finding in a controlled clinical setting does not make ayahuasca an approved or advisable treatment outside of research. Legally, ayahuasca contains DMT, a strictly scheduled substance in most jurisdictions, with limited exemptions for recognized ritual practice in select regions. The most balanced takeaway is that this is a promising avenue of clinical research warranting deeper study—neither a miraculous cure-all nor a hazard to be dismissed out of hand.
Source
- Palhano-Fontes F, et al. Rapid antidepressant effects of the psychedelic ayahuasca in treatment-resistant depression: a randomized placebo-controlled trial. Psychological Medicine, 2019;49(4):655-663. DOI: 10.1017/S0033291718001356
Educational content written from a harm reduction perspective and with respect for individual freedom. It is not a substitute for advice from a healthcare professional and is not intended to encourage or condemn any drug use.
