The relation between naturalistic use of psychedelics and perception of emotional stimuli: An event-related potential study comparing non-users and experienced users of classic psychedelics

Background: Previous research has suggested that controlled administration of psychedelic substances can modulate emotional reactivity, enhancing positive and diminishing negative emotions. However, it is unclear whether similar effects are associated with using psychedelics in less-controlled naturalistic environments.Aims: This cross-sectional study investigated the neural markers associated with the perception of emotional stimuli in individuals with extensive experience of naturalistic psychedelic use (15 or more lifetime experiences), comparing them to non-users. Methods: Electroencephalography (EEG) signals were recorded from two groups: experienced psychedelics users (N = 56) and non-users (N = 55). Participants were presented with facial images depicting neutral or emotional expressions (anger, sadness, and happiness). Event-related potential (ERP) components were analyzed as indices of emotional reactivity. Results: Psychedelic users were characterized by significantly lower amplitudes of the N200 component in response to fearful faces, in comparison to non-users. In addition, interaction effects between Group and Emotional expression were observed on N170 and N200 amplitudes, indicating group differences in the processing of fearful faces. However, no significant between-group differences emerged in the analysis of later ERP components associated with attention and cognitive processes (P200 and P300). Conclusions: The results suggest that naturalistic use of psychedelics may be linked to reduced reactivity to emotionally negative stimuli at the early and automatic processing stages. Our study contributes to a better understanding of the effects related to using psychedelics in naturalistic contexts.