Safety, Therapeutic Potential, and Mechanisms of Two Psilocybin Doses, Administered With Psychological Support in Young Adults With Anorexia Nervosa

The goal of this clinical trial is to learn if psilocybin, given with psychological support, is safe and helps treat anorexia nervosa in young adults. Anorexia nervosa is a serious eating disorder that currently has no approved medicine. Psilocybin is a psychedelic substance that may help the brain form new connections, which could make it easier for people with anorexia nervosa to develop healthier ways of thinking. The main questions this study aims to answer are: * Is psilocybin with psychological support safe and well-tolerated? * Does psilocybin with psychological support help lower symptoms of anorexia nervosa? * How might psilocybin work in the brain to support recovery from anorexia? This study will compare psilocybin with psychological support to Treatment as Usual (TAU). Participants in the study will be randomly placed into one of the two groups. There will be 40 patients with anorexia nervosa included, 20 per group. TAU includes the standard care people receive for anorexia nervosa in a specialized eating disorder clinic in Region Skåne, Sweden. Participants will: * Be between 16 and 35 years old and have anorexia nervosa * Take psilocybin (25 mg) by mouth two times, four weeks apart * Receive psychological support before, during, and after each dosing session (including preparation and integration sessions) * Complete questionnaires, have brain scans (magnetic resonance imaging) and blood tests to learn more about how psilocybin may work * Share their personal experiences as part of a qualitative interview This study hopes to learn if psilocybin, when given with the right support, can be a helpful and safe option for people living with anorexia nervosa.