This Phase II interventional trial (n=12) will evaluate the effects of psilocybin (25 mg) with and without risperidone (1 mg) on synaptic density in adults with treatment-resistant depression (TRD).
This non-randomised, sequential, Phase II trial will assess whether a single oral dose of psilocybin 25 mg, given with or without risperidone 1 mg, is associated with changes in synaptic density measured by an SV2A PET radiotracer in adults with treatment-resistant depression.
Participants receive supportive therapy; imaging feasibility, safety, and associations between PET SV2A measures and antidepressant response are primary aims. Two experimental arms compare psilocybin alone versus risperidone pre-treatment plus psilocybin; masking is open-label (none).
Risperidone 1 mg given 60 minutes before psilocybin 25 mg; single administration with supportive therapy and PET imaging.
Risperidone 1 mg given 60 minutes before psilocybin; recorded as active concomitant drug
Single oral dose of psilocybin 25 mg with supportive therapy and PET imaging.