Clinical practice and trial protocols identify specific groups for whom psychedelic-assisted therapy is likely unsafe or inappropriate. Screening and exclusion aim to reduce the risk of psychiatric destabilization, medical complications, and adverse drug interactions while respecting cultural and legal differences in access.
Clinical and psychiatric contraindications
Most guidelines emphasize excluding people with current or a strong personal or family history of psychotic disorders or schizophrenia because classic serotonergic psychedelics can precipitate or worsen psychosis. Roland R. Griffiths Johns Hopkins University and Matthew W. Johnson Johns Hopkins University have described screening procedures that prioritize psychosis risk to prevent serious psychiatric adverse events. People with bipolar I disorder are commonly contraindicated because stimulatory psychedelic experiences can trigger manic episodes, a point stressed in clinical trial inclusion criteria used by researchers at Imperial College London led by Robin Carhart-Harris. A history of severe, uncontrolled mood instability changes the risk–benefit calculus from therapeutic to dangerous.
Medical and medication-related contraindications
Cardiovascular disease and uncontrolled hypertension are frequent medical exclusions because psychedelics and MDMA raise heart rate and blood pressure, increasing the risk of arrhythmia or ischemia. Michael Mithoefer Multidisciplinary Association for Psychedelic Studies and other investigators in MDMA-assisted therapy trials developed detailed medical screens to identify these risks. Concurrent use of serotonergic medications such as selective serotonin reuptake inhibitors may blunt psychedelic therapeutic effects and, in some combinations, increase the risk of serotonin syndrome. Monoamine oxidase inhibitor interactions are particularly hazardous with naturally occurring DMT in ayahuasca, a concern emphasized in pharmacology reviews by researchers at Johns Hopkins University. Pregnancy and breastfeeding are generally contraindicated because fetal and neonatal risks are not well characterized; ethical and safety standards in trials exclude these groups.
Cultural, territorial, and legal nuances affect who actually receives psychedelic therapies. Indigenous communities have long ceremonial uses of plant psychedelics, which raises questions about cultural competence and territorial rights when Western clinical models expand. Legal restrictions in many countries and differences between state and federal laws in the United States further influence access and screening practices, with research organizations adapting protocols to local regulation.
Consequences of ignoring contraindications include psychiatric hospitalization, cardiovascular events, worsened long-term outcomes, and legal repercussions. Established protocols from leading institutions such as Johns Hopkins University, Imperial College London, and the Multidisciplinary Association for Psychedelic Studies emphasize careful screening, multidisciplinary assessment, and culturally informed consent to minimize these harms. Appropriate exclusion is not denial of care but a safety measure while evidence evolves.