One can only speculate at this point. Rick Strassman alludes to the idea that since DMT is endogenously created, theoretically by the pineal gland, and he also links this theory up to NDEs, that there MIGHT be a cascade of endogenously created DMT that floods the brain when humans are under tremendously stress, i.e., near dying/death. Again, it's Strassman's theory partially laid out in The Spirit Molecule, but there is no scientific evidence to back it up...only anecdotes and speculation. It is an interesting theory, of course, but again, it would take a tremendously feat of science and data collection to prove such a thing, hypothetically.