Psilocybin, the psychedelic substance found in magic mushrooms, is a promising new treatment for psychiatric disorders, especially depression. The beneficial effects on mood and anxiety of psilocybin are rapid and pronounced after just a single treatment. A small study even suggested that these benefits remain after a year. But what is really needed is a comparison of the long-term effect of psilocybin with another treatment (an antidepressant) or a placebo. Ideally, neither participants nor staff should be aware of who was given what – this is known as “double blind” and is used to remove bia…