By Fernanda Palhano-Fontes,Dayanna BarretoHeloisa OniasKatia C. Andrade

In a recent open-label trial, 17 patients with major depressive disorder attended a single dosing session with ayahuasca. Depression severity was assessed before, during and after dosing, using the Hamilton Depression Rating scale (HAM-D) and the Montgomery–Åsberg Depression Rating Scale (MADRS) (Sanches et al., 2016). Significant reduction in depression severity was found already in the first hours after dosing, an effect that remained significant for 21 days (Osório et al., 2015; Sanches et al., 2016). Although promising, these studies have not controlled for the placebo effect, which can be remarkably high in clinical trials for depression, reaching 30–40% of the patients (Sonawalla and Rosenbaum, 2002). To address this issue, and to further test the antidepressant effects of ayahuasca, we conducted a randomized placebo-controlled trial in patients with treatment-resistant depression. Additionally, we explored for correlations between the antidepressant and the acute effects of ayahuasca.