Terence mcKenna was/is probably the most known DMT fan around the world (him and Tim Leary) and Terence was no boy scout when it came to psychedelics and exploring the "inside world". and even he said that it's something he cant do every week. if i remember correctly he said once a month was the most he could take.
Apperantly the human brain produces DMT in certain sleep cycles and large amounts of it in near-death experiences. There's a book called "DMT: The Spirit Molecule" by DR. Richard Straussman that's supposed to be good. (i havent read it, but i've heard some of his very interesting interviews.) He was like the only person that had the governments permission to do tests on it
also, some people say that DMT and Ayauascha (that has DMT in it) can be used to break people's cokaine/nicotine/heroin/alcohol addictions. I heard there's some clinic in some country where they have a medical doctor, a psychiatrist, and a fuckin shaman present during the "detox program" haha
lol another thing, some funny christians believe that meditation, weed, and other psychedelic drugs opens the gate ways so a demon can posses you. lol. it's like no no no dont try to get in touch with yourself but listen to the child molestor fish head, and go kill some pagans