A systematic review of 39 papers examined whether classic psychedelics can cause anxiety and affective disorders, finding that persistent problems are rare and typically occur in people with multiple risk factors such as overdose, polydrug use, unstructured recreational settings, psychosocial stress, or personal or family psychiatric history. In clinical psychedelic-assisted therapy, enduring anxiety or mood symptoms were uncommon; acute anxiety that arose during sessions usually resolved on its own without extra treatment. The role of emotional catharsis in therapy is discussed. Recommendations to improve safety include strengthening the therapeutic alliance, ensuring adequate mental preparation, acclimating to high doses, and providing ongoing therapeutic support.
A systematic review of 54 studies found that the intensity of the acute psychedelic experience, particularly mystical-type experiences, is the most frequently reported predictor of therapeutic response in psychedelic-assisted therapy for mental disorders, though this was not consistent across all disorders or time points. Factors related to set, setting, and dose were associated with the likelihood and intensity of these experiences. The review included adult populations with substance-use disorders, major depressive disorder, anxiety disorders, obsessive-compulsive disorder, post-traumatic stress disorder, and existential distress, as well as naturalistic samples.