Over the past decade, psychedelics have moved from the margins of psychiatry into some of the world's leading academic centres, where they are being investigated for conditions ranging from treatment-resistant depression and post-traumatic stress disorder (PTSD) to addiction, anorexia nervosa and end-of-life anxiety. The results have generated real excitement, particularly for psilocybin, where several large studies have shown rapid and sometimes sustained benefits after only one or two administ