A systematic review of 34 experimental studies on classic psychedelics with follow-up periods of at least two weeks found lasting changes in personality, attitudes, depression, spirituality, anxiety, wellbeing, substance misuse, meditative practices, and mindfulness. Psilocybin was the most commonly administered drug. Mystical experiences, connectedness, emotional breakthrough, and increased neural entropy were linked to these long-term psychological changes. With proper screening, preparation, supervision, and integration, participants reported few aversive side effects. The review calls for larger, more diverse samples, longer longitudinal designs, stronger control conditions, and standardized dosages in future research.
People who are more open, accepting, and prone to absorption, as well as those who enter a psychedelic session with a mindset of surrender, are more likely to have positive, mystical-type experiences. Conversely, individuals who are low in openness or surrender, or who arrive in a preoccupied, apprehensive, or confused state, are more likely to experience adverse reactions. A systematic review of 14 studies found that sex is not a robust predictor of drug effects, but certain brain-based measures—such as 5-HT2AR binding potential, executive network node diversity, and rACC volume—may serve as biomarkers. Older age and prior experience with psychedelics are linked to less intense effects, suggesting users may become slightly less sensitive after repeated use.