In a study reported in the Journal of Psychopharmacology (Sep 2011), 51 people had 2-5 sessions of psilocybin or “magic mushrooms.” Of these, 30 people had mystical experiences. The people who had mystical experiences showed changes on one personality trait that persisted even a year later. They showed greater “openness” to feelings, ideas, values, aesthetic appreciation, creativity, imagination, and curiosity.
Four personality traits that did not change were “extroversion,” “neuroticism,” agreeableness,” and “conscientiousness.”
The implication is that very limited exposure to a naturally-occurring neuroactive substance caused a psi experience for some people, and those same people then showed persistent neurological changes afterwards. I’d like to know if they also showed a persistent increase in psi experiences afterwards. Note that the personality trait that changed is compatible with being more open to psychic perception.