"Both [psychonauts and Christians] could teach the other something. Mark Juhan, a lay chaplain and psychonaut — rare hybrid — suggests that psychedelics can rescue Christians from an over-heavy dependence on Scripturalism at the cost of a personal encounter with the Divine. They can also teach Christians a greater reverence for God's creation in nature, which could include such extraordinary plants. I also think the psychedelic community is admirably tolerant of difference.
Psychonauts, on the other hand, could learn from Christians how to turn altered states into altered traits (as the theologian Huston Smith put it). They could learn how to ground ecstatic experiences in community, and in charitable work. They could also learn from Christian mysticism how to practice discernment of spirits, how to avoid ego-inflation, how to practice a theology deeper than simply saying 'well that was far out'. And they could learn, perhaps, to overcome a fetishization of substances and experiences (Leary's 'religion of LSD') and a more mature confrontation with the givens of suffering and death.
Jules Evans, British philosopher, author and (not so long, a couple of years perhaps, as I understood it, after a trip to the Amazon where he tested ayahuasca) ambassador for mind-expanding drugs. The medications of psychiatry, on the one hand, and the common drugs in society, on the other, are heard a lot about. For and against. If you want to orient yourself on Evans (a third?) area – mystical experiences/spirituality & substances – then he is a good introductor.