Effects of Ayahuasca on the Recognition of Facial Expressions of Emotions in Naive Healthy Volunteers

A single dose of ayahuasca did not alter the recognition of emotions in facial expressions compared with placebo in healthy volunteers. The drug was well tolerated, producing nausea, gastrointestinal discomfort, and vomiting, with some reports of visual effects, tranquility, and well-being, and few reports of transient anxiety or confusion. No significant effects appeared on cardiovascular measures or brain-derived neurotrophic factor levels. A significant time-dependent deterioration of alkaloids, especially dimethyltryptamine, was observed. The absence of effects on emotion recognition may stem from the dose used, alkaloid degradation, learning effects, or the sample's high educational level.

Study at a glance

Abstract

Abstract 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.