Pilot Proof of Concept Study Evaluating the Potential Psilocybin Assisted Psychotherapy (PAP) as a Therapeutic Tool for Patients Suffering From Severe Irritable Bowel Syndrome.

This study will serve as a pilot randomized controlled trial to assess the feasibility of Psilocybin-Assisted Psychotherapy (PAP) in Treating Irritable Bowel Syndrome (IBS). Patients with severe IBS will undergo 3 pre-psychotherapy sessions with two licensed and trained psychedelic therapists, then will be randomized to undergo a guided psychotherapy session with single 25 mg oral "high" dose of psilocybin or a single 100 mg dose of niacin (active placebo) and attend 4 post-therapy integration sessions.