The supplementary material for this article can be found at https://doi.org/10.1017/S0033291718001356

The authors would like to express their gratitude to all patients who volunteered for this experiment. To the Brain Institute and to the Hospital Universitário Onofre Lopes (HUOL), both from the Federal University of Rio Grande do Norte (UFRN) for always giving the necessary institutional support. To the laboratory of Pharmacognosy for helping with placebo preparation. To Edilsom Fernandes, for carefully preparing the Ayahuasca batch used in our study, and for the fruitful discussion, particularly about the dosing session. To Sidarta Ribeiro, for the enthusiastic support throughout the study. To Dr Ricardo Lagreca, for the unconditional support. To Beatriz Labate, for the fruitful discussions. To Altay Souza and João Sato for assistance with statistical analysis. To Deborah Maia, Ranna Brito, Tayrine Lopes, Lízie Brasileiro, Artur Morais, Isaac Campos, Brígida Albuquerque, Marianna Lucena, Fernanda Araújo, Raíssa Nóbrega, Marina Leonardo, Kaique Andrade, Rodolfo Lira, Giuliana Travassos, for helping with data acquisition. To Prof. Octávio Pontes-Neto and Adriano Tort for critical review of the manuscript. To the Brazilian federal funding agencies CNPq (grants #466760/2014 & #479466/2013) and CAPES (grants #1677/2012 & #1577/2013) for providing financial support.

FPF, KCA, NGC, BLS, JR, JCA, LFT, SAMR, FO, RS, JAC, JH, EA, JPMO, and DBA contributed to study design and conception. FRRS and AASJ conceived and developed the substance used as placebo. GOS and MY conducted the analysis to determine alkaloid concentrations. JA coordinated the psychology team. NGC coordinated the biochemistry team. DB, EA, and JPMO recruited the patients. FPF, HO, KCA, MN, JP, BA, and DBA coordinated data acquisition. DBA coordinated the trial. FPF, HO, KCA, MN, JP, JPMO, and DBA analyzed data and interpreted the results. FPF, HO, KCA, MN, JP, and DBA were responsible for the first draft of the manuscript. All authors read, critically revised, and approved the manuscript.

This study was funded by the Brazilian National Council for Scientific and Technological Development (CNPq, grants #466760/2014 & #479466/2013), and by the CAPES Foundation within the Ministry of Education (grants #1677/2012 & #1577/2013). The authors declare no competing financial interests.

The authors assert that all procedures contributing to this work comply with the ethical standards of the relevant national and institutional committees on human experimentation and with the Helsinki Declaration of 1975, as revised in 2008.

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