Therapeutic potential of psilocybin in the pharmacological treatment of obsessive-compulsive disorder: a scoping review protocol.

Obsessive-compulsive disorder (OCD) is a chronic neuropsychiatric condition characterized by intrusive thoughts and repetitive behaviors that cause distress and functional impairment worldwide. Although selective serotonin reuptake inhibitors and cognitive behavioral therapy are first-line treatments, a considerable proportion of patients show an insufficient response, supporting the need for alternative pharmacological strategies. Psilocybin, a classic psychedelic metabolized into psilocin, has sparked interest for its activity in serotonergic pathways, especially 5-HT2A receptors, and its potential effects on neuroplasticity and brain network modulation. This scoping review aims to identify, characterize, and synthesize the available scientific evidence on the therapeutic potential of psilocybin in the pharmacological treatment of OCD, including preclinical findings, proposed mechanisms of action, and clinical evidence. The review will be conducted in accordance with the JBI recommendations and the data will be reported using the PRISMA-ScR checklist. Searches will be conducted in PubMed, Scopus, and Web of Science, with no language or publication date restrictions. Eligible studies will include preclinical and clinical research evaluating psilocybin or psilocin for OCD. The findings are expected to map current evidence, identify knowledge gaps, and guide future research on psilocybin as a potential therapeutic strategy for OCD, especially in patients with treatment-resistant symptoms and persistent impairment despite available standard interventions.