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Background: Recognition of emotions in facial expressions (REFE) is a key aspect of social cognition. Anxiety and mood disorders are associated with deficits in REFE, and anxiolytics and antidepressants reverse these deficits. Recent studies have shown that serotonergic hallucinogens (i.e. ayahuasca, dimethyltryptamine, psilocybin, lysergic acid diethylamide [LSD], and mescaline) have anxiolytic and antidepressant properties, but their effects on REFE are not well understood. The purpose of the study was to conduct a systematic review analyzing the effects of serotonergic hallucinogens on REFE in humans. Methods: Studies published in the PubMed, PsycINFO, and Web of Science databases until 19 October 2018 which analyzed the effects of serotonergic hallucinogens on REFE in humans were included. Results: Of the 62 studies identified, 8 studies were included. Included studies involved the administration of a single or a few doses of LSD or psilocybin, and most trials were randomized and controlled with placebo. LSD and psilocybin reduced the recognition of negative emotions in most studies and modulated amygdala activity to these stimuli, which was correlated with antidepressive effects in patients. Both drugs were well tolerated. Conclusions: Serotonergic hallucinogens reduced the recognition of negative emotions by modulating amygdala activity. Despite the small sample sizes, results suggest that serotonergic hallucinogens show promising beneficial effects on deficits in REFE.

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Psychedelics or serotonergic hallucinogens are a group of substances that share the agonism of serotonergic 5-HT 2A receptors as their main mechanism of action. Its main effects include changes in perception, cognitive process, and mood. Despite being used for centuries by different cultures in ritual contexts, these substances have currently aroused the interest of science and industry for their promising antidepressant, anxiolytic, and anti-addictive effects. Considering this evidence, this article aims to explore some of the possible health policy challenges to integrate these therapeutic tools into broad and heterogeneous health systems. As a main benefit, these substances produce rapid and enduring effects with the administration of single or few doses, which could lead to new treatment possibilities for patients with severe mental disorders resistant to the usual medications. The main challenge is associated with the fact that these substances remain scheduled in most countries and are associated with social stigma related to their recreational use (especially LSD and psilocybin). This situation makes it exceedingly difficult to conduct clinical trials, although international conventions allow such research. Ethically, this could be interpreted as a violation of human rights since thousands of people are prevented from having access to possible benefits. Interestingly, ritual ayahuasca use is more acceptable to the public than the use of psilocybin-containing mushrooms or LSD. The controlled, clinical use of LSD and psilocybin seems to be less criticized and is being explored by the industry. Rigorous scientific evidence coupled with industrial interests (LSD and psilocybin), together with respect for traditional uses (ayahuasca) and international conventions, seems to be the best way for these drugs to be integrated into health systems in the next years. Which highlights the need for an urgent dialogue between science, health system, society, and politics.