Psychedelics (Greek: psyche – soul; delos – reveal, manifest) are a group of psychoactive substances (partly including dissociatives and deliriants) altering (consciousness), the manner of thinking, and how emotions are experienced. What sets psychedelics apart from other psychoactive substances (stimulants, depressants) is their ability to alter the state and content of consciousness (Bayne & Carter, 2018). Experiences they induce are often compared to altered states of consciousness such as dreams (Kraehenmann, 2017; Millière et al., 2018), hypnosis (Lemercier & Terhune, 2018) and meditation (Millière, Carhart-Harris, Roseman, Trautwein, & Berkovich-Ohana, 2018). The classic psychedelics include psilocybin (psilocybin-containing mushrooms), DMT (e.g. ayahuasca), mescaline (cacti such as San Pedro and peyote) and LSD (lysergic acid diethylamide; Johnson, Hendricks, Barrett, & Griffiths, 2019). Psychedelics may positively impact the psychological well-being of patients and healthy subjects (Nichols, Johnson, & Nichols, 2017; MacLean, Johnson, & Griffiths, 2011). For instance, during a study at the John Hopkins School of Medicine, 58% of participants rated the psilocybin-occasioned experience as being among the five most personally meaningful ones. The majority of them emphasized that this experience allowed them to better understand themselves and have more compassion and patience towards other people (Griffiths, Richards, Johnson, McCann, & Jesse, 2008). A subsequent study confirmed that even a single intake of psilocybin can lead to permanent changes in personality, resulting in increased openness (MacLean et al., 2011). At the same time, it should be noted that psychedelic substances taken in uncontrolled conditions (outside the research and medical environment) can lead to negative psychological effects and risky behaviours (Carbonaro et al., 2016; Johnson, Richards, & Griffiths, 2008).