At the end of the day, no matter what our society has decided to label them psychedelics are entheogens and have been used for thousands of years for many purposes including healing.
I find it really weird people both in and out of the scientific and medical fields are shocked when they "discover" positive results in a healing context. It stems from this arrogant mentality that "no ancient society has ever been as advanced or as smart as us!", when in reality, it has been more advanced before, just in different ways as they took different routes and made different decisions.
It's known as ''psychedelic therapy" now, and of course is extremely promising. The problem is getting permission to conduct trials is very hard, and sometimes next to impossible with certain substances. Mushrooms, Ibogaine, DMT, Cannabis, Mescaline and more are all extremely useful medicinally when used right. The trials that have been allowed have been highly successful. Another problem is pharmaceutical companies would rather extract, separate and modify natural (free) substances and chemicals in order to put them into a form that is more marketable and profitable. They do this under the guise of making it "safer", but safety with this stuff is not about the plants/mushrooms themselves, rather the context in which they are used.
Certain synthetics are also of course promising (LSD, MDA...), but it's mostly because they are chemical cousins of already existing natural substances.
http://www.amazon.com/Plants-Gods-Sacre ... 0892814063
http://www.huliq.com/10559/magic-mushro ... -headaches
http://www.time.com/time/health/article ... 87,00.html
http://www.houstonpress.com/2010-11-18/ ... he-junkie/
http://www.cbsnews.com/8301-504763_162- ... ssion-how/
http://www.stuff.co.nz/life-style/wellb ... depression
http://www.telegraph.co.uk/health/healt ... ssion.html