DMT is as natural as (and similar in a molecular sense to) Seratonin and Melatonin. It is found organically in our neuro-chemistry as well as other mammals and plants around the world. The blood brain barrier is quite picky about what it lets through so the assumption is that there's a purpose for this molecule though quite what that purpose is , nobody seems to know for sure.
After the Americans shut down all psychedelic research in the late 60's, possibly because of the connection to war protests, it became career suicide to even express an interest in the subject worldwide, but some time in the mid 90's Dr. Rick Strassman began clinical trials to observe the effects of DMT from a standard psycho-pharmacological model to about 60 people over about five years.
The interviews are on Youtube but if the chance avails itself you can find out more about screenings at the Spirit Molecule website.