I watched a documentary yesterday about hallucinogenic plants, always a fascinating subject. (It was called 'From Peyote to LSD'). The documentary dealt largely with indiginous tribes of North and South America and their use of hallucinogenic plants in healing rituals. Peyote for example, is often used to treat alcoholism. At first, I couldn't really conceive of hallucingens having healing powers, aside from perhaps increasing spiritual growth and thus overall well-being. But then some of the healers/shamans spoke of the specifics of the guided visionary experience.
First of all, the experience is surrounded with sacred rituals, such as purification, incense burning, chanting, etc. This alone would set up the state of mind for a very intense experience. Anyone who's done hallucinogens understands the extent to which your environment plays a role in the quality of your trip. Then both the healer, the sufferer and any other participants ingest the hallucinogenic plant(s), and the healer serves as a guide on the ensuing journey. From this point on, the participants have entered the "spirit world", which I believe can also be understood as the psyche or the realm of archetypes. In our minds, concepts such as fear or courage are represented by archetypal images, such as a wolf or a lion. During a hallucinogenic journey, these images can be directly confronted and experienced.
In the case of healing, it appears to me that with the guidance of the shaman or healer, the illness of the sufferer is personified by an archetypal image, such as a wolf. In the documentary, one helaer spoke of "confronting and defeating the wolf". I expect you yourself are personified as an image as well, such as your spirit animal. (Animals are the most common symbols for these rituals). Then with the help of the healer, who directs you and guides you, a journey unfolds, a quest inside of your own body and mind. The end result is the defeat of the wolf, the illness.
You have to ask yourself, what sort of effect would experiencing this intense scenario have on a person? My personal belief is that it would be a very effective method of healing. It is like affirmations and visulizations, but it is far superior. The body does have the ability to heal itself. There have been cases of people curing themselves of cancer without any western medicine using visulization. One woman who had breast cancer constantly visualized white blood cells enteing her tumor, which did in fact disappear. Similarly, a man with a brain tumor visulaized his white blood cells as star wars x-wing fighters attacking the tumor. His tumor disappeared as well. Incredible, obviously. So going through this intense visionary experience, where you literally do battle with the illness that is living inside you, and you defeat it... that's got to have an incredible effect on the body and the mind. Fucking intense!