This randomized, double-blind, placebo-controlled, pilot study (n=22) investigated the acute and prolonged effects of ayahuasca (9.36mg of DMT, 79.62mg of harmine, 50.71mg of tetrahydroharmine, 7.38mg of harmaline) on social cognition amongst healthy volunteers. Contrary to previous studies which indicate that psychedelics reduce the recognition of fearful face stimuli, this study yielded null results in the absence of ayahuasca-induced effects on the recognition of emotions in facial expressions.
“Background: The recognition of emotions in facial expressions (REFE) is a core aspect of social cognition. Previous studies with the serotonergic hallucinogens lysergic acid diethylamide and psilocybin showed that these drugs reduced the recognition of negative (fear) faces in healthy volunteers. This trial assessed the acute and prolonged effects of a single dose of ayahuasca on the REFE.
Methods: Twenty-two healthy volunteers participated in a pilot, proof-of-concept, randomized trial. Study variables included a REFE task performed before and 4 hours after drug intake, subjective effects (self-reports/observer impressions), tolerability measures (cardiovascular measures, self-reports), and brain-derived neurotrophic factor plasma levels. The REFE task was applied again 1, 7, 14, and 21 days and 3 months after drug intake. Stability of ayahuasca alkaloids during the study was also assessed (room temperature, 18 months).
Findings: Compared with placebo, ayahuasca did not modify the REFE. No significant effects were observed on cardiovascular measures and brain-derived neurotrophic factor levels. Volunteers reported visual effects, tranquility/relaxation, and well-being, with few reports of transient anxiety/confusion. Ayahuasca was well tolerated, producing mainly nausea, gastrointestinal discomfort, and vomiting. A significant time-dependent deterioration of alkaloids was observed, especially for dimethyltryptamine.
Conclusions: Absence of significant effects on the REFE task could be due to lack of effects of ayahuasca (at the doses used), alkaloid degradation, learning effects, and the high educational level of the sample. Further trials with different samples are needed to better understand the effects of ayahuasca and other serotonergic hallucinogens on the REFE. Future trials should improve methods to guarantee the stability of ayahuasca alkaloids.”
Authors: Juliana M. Rocha, Giordano N. Rossi, Flávia de Lima Osório, José Carlos Bouso, Gabriela de Oliveira Silveira, Mauricio Yonamine, Alline Cristina Campos, Giuliana Bertozi, Hallak Jaime E. Cecílio & Rafael G. Dos Santos
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Journal of Clinical Psychopharmacology
April 8, 2021