AbstractBackgroundRecent open-label trials show that psychedelics, such as ayahuasca, hold promise as fast-onset antidepressants in treatment-resistant depression.MethodsTo test the antidepressant effects of ayahuasca, we conducted a parallel-arm, double-blind randomized placebo-controlled trial in 29 patients with treatment-resistant depression. Patients received a single dose of either ayahuasca or placebo. We assessed changes in depression severity with the Montgomery-Åsberg Depression Rating Scale (MADRS) and the Hamilton Depression Rating scale at baseline, and at 1 (D1), 2 (D2), and 7 (D7) days after dosing.ResultsWe observed significant antidepressant effects of ayahuasca when compared with placebo at all-time points. MADRS scores were significantly lower in the ayahuasca group compared with placebo at D1 and D2 (p= 0.04), and at D7 (p< 0.0001). Between-group effect sizes increased from D1 to D7 (D1: Cohen'sd= 0.84; D2: Cohen'sd= 0.84; D7: Cohen'sd= 1.49). Response rates were high for both groups at D1 and D2, and significantly higher in the ayahuasca group at D7 (64%v.27%;p= 0.04). Remission rate showed a trend toward significance at D7 (36%v.7%,p= 0.054).ConclusionsTo our knowledge, this is the first controlled trial to test a psychedelic substance in treatment-resistant depression. Overall, this study brings new evidence supporting the safety and therapeutic value of ayahuasca, dosed within an appropriate setting, to help treat depression. This study is registered athttp://clinicaltrials.gov(NCT02914769).