Current research suggests that, with proper screening protocols (e.g., the exclusion of people with a personal or family history of psychosis), psychedelic therapy is quite safe. Although side effects can occur during the psychedelic session, they are generally short-term and resolve soon after the medication’s effects have worn off; these include anxiety, nausea, vomiting (particularly in the case of ayahuasca), headache, and mild increases in blood pressure and heart rate.[1][2]
Psychedelics produce profound short-term psychological effects when consumed in full doses, including changes in thinking, perception, sense of self, and emotions (positive and negative) that may lead to mystical/spiritual experiences and an increased sense of social connectedness. While these “side effects” might be uncomfortable for some people, they are suggested to be an important component of the therapeutic effect of psychedelic therapy.[2]
A rare possible side effect that has been identified in case reports is hallucinogen persisting perception disorder (HPPD), which is when perceptual disturbances experienced while under the influence of psychoactive drugs (e.g., classic psychedelics, cannabis, MDMA) re-emerge after the drug's effects have worn off. This might include visual “flashbacks” or other disturbances like visual snow (grainy, pixelated vision) or floaters. HPPD has not been reported in any psychedelic therapy studies and the true risk is not clear.[3][4]