Earlier this month Rolling Stone published an article about the clinical use of psychedelics in underground clinics.* It's an interesting read and delves in the motivations and experiences of a number of medical and allied professionals who opt to provide such agents as MDMA, ayahuasca, or magic mushroms (containing psilocybin) in unregulated settings. That professionals will take on potential legal risk from practicing with these substances is a testament to their belief that they work, and something that is being gradually backed up by high quality scientific studies. Several organizations are working on this process to formally medicalize these agents and bring them to legal clinical use, such as Hefter, MAPS, and others (see my resources page for links and more reading). The available clinical data suggests that the classical hallucinogens such as psilocybin, LSD, and ayahuasca (which contains DMT) may have greater efficacy and duration of effect for depression and processing trauma, but it is hard to say concretely without further clinical trials, several of which are in the process due to the efforts of the above mentioned organizations. Until that time, it seems that ketamine is the only clinically available (and legal) psychedlic available.
*As as aside, Rolling Stone labels psychedelics as "miracle", which I am always hesitant to endorse as such. The clinical trial data thus far shows large effect sizes and a relatively benign side effect profile, though with the caveat that these outcomes are carefully structured and take place in controlled medical settings. As the article mentions, based on the authors personal account of several illicit psychedelic treatments, there can be significant personal turmoil during the healing and integration process; such treatments are not without their risks, and it is very likely that such treatments will not work for everyone. There does, however, seem to be a correlation between subjects who achieve a mystical experience and better treatment outcomes, at least with the classical hallucinogens. So perhaps it is more appropriate to term it "a miraculous experience"?