To the best of my Knowledge marijuana isn't all that widely used by Shamanic peoples of the world, they are more into he vines roots and fungi. One tribe comes to mind that came from Mexico that uses Cannabis in their belief system but my brain can't squeeze out any more than that besides their belief system is a blend of Christianity and traditional beliefs. Good book to check out regarding psychoactive substances and tribal traditions concerning them is called "Plants of the Gods" or something like that, has a short chapter on all the various vegetation involved with the tribal people of the world.