Psilocybin-Assisted Group Integration Psychotherapy for Treatment-Resistant Depression

Inclusion Criteria: * Must be deemed to have capacity to provide informed consent; * Must sign and date the informed consent form; * Stated willingness to comply with all study procedures; * Stated willingness to comply with group integration requirements (i.e., maintaining confidentiality of other group members and group etiquette); * Stated willingness to commit to attending all group sessions. Of note, participants who miss a group session will not be penalized, provided they have communicated their anticipated or unanticipated absence with the study therapist(s); * Ability to read and communicate in English, such that their literacy and comprehension is sufficient for understanding the consent form, study questionnaires and group participation, as evaluated by study staff obtaining consent; * Met all the inclusion criteria and none of the exclusion criteria of either the PSI-1V2 or Psilo-BD clinical trials. * Completed the Primary Endpoint measures as part of the PSI-1V2 or Psilo-BD clinical trials. * Participants who are actively receiving therapy outside of this study are eligible to participate, provided the external therapy they are receiving is not psilocybin-assisted group integration psychotherapy. Exclusion Criteria: * Active suicidal ideation as determined by the C-SSRS and/or clinical interview (significant suicide risk is defined by suicidal ideation as endorsed by items 4 or 5 of the C-SSRS) or active suicidality requiring involuntary inpatient treatment or recent suicide attempts within the past month; * Withdrawal, dropout, loss to follow-up, or demonstrated significant study intervention non-compliance of either the PSI-1V2 or Psilo-BD clinical trials. * Any behaviors that, in the opinion of the investigator, may interfere with the group therapy model (e.g., participants in acute crisis, demonstrated resistance to the therapeutic process of the main clinical trials, etc.); * Participants who are actively receiving psilocybin-assisted group integration psychotherapy outside of the study.