A review of nine small clinical trials found that ayahuasca and psilocybin, when used to treat major depressive disorder and treatment-resistant depression, are associated with changes in several biological markers. These include increased serum brain-derived neurotrophic factor, decreased serum C-reactive protein, altered amygdala activation, and changes in functional connectivity between brain regions such as the ventromedial prefrontal cortex, anterior cingulate cortex, and posterior cingulate cortex. These associations suggest potential mechanisms of clinical response, but larger, longer-term studies are needed to confirm these findings.
Up to 60% of people with obsessive–compulsive disorder (OCD) do not respond to standard treatments such as selective serotonin reuptake inhibitors, antipsychotic augmentation, or cognitive–behavioural therapy. This open-label pilot trial will test whether a single 25 mg dose of psilocybin combined with psychological support is feasible, tolerable, and safe for ten adults with treatment-resistant OCD. Clinical improvement will be measured with the Yale–Brown Obsessive–Compulsive Scale. Exploratory brain imaging, electroencephalogram, and transcranial magnetic stimulation-electroencephalogram measures will examine changes in dynamic connectivity and brain dynamics before, during, and up to one week after dosing. Results will inform the design of larger randomized trials and help clarify neurobiological mechanisms of psilocybin-assisted therapy.