An observational study in Treatment Resistant Depression and Depression - Major Depressive Disorder, sponsored by Unity Health Toronto. Recruiting at 1 site in Canada. Open to participants aged 25 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-15.
Sponsored by Unity Health Toronto · Observational
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Among 76 studies in Depressive Disorder, Treatment-Resistant with a site in Canada — 29 open to participants now, 36 under way, 7 of them phase 3. Depressive Disorder, Treatment-Resistant · Canada.
Among the 76 studies in Depressive Disorder, Treatment-Resistant with a site in Canada, this one is one of 11 that started in 2025, is one of 6 observational ones, reaches primary completion later than 28 of the 35 other live ones, and was the 16th registered.
448 studies on the registry are indexed under Depressive Disorder, Treatment-Resistant; 147 are open to participants now.
Browse Depressive Disorder, Treatment-Resistant studies →29 of the 76 studies in Depressive Disorder, Treatment-Resistant with a site in Canada are open now. Recruiting first, the newest first:
The Royal's Institute of Mental Health Research · Sites in Canada
Ages 18–65
Sunnybrook Health Sciences Centre · Sites in Canada
Ages 18–65
Joshua Rosenblat · Sites in Canada
Ages 18–70
Centre for Addiction and Mental Health · Sites in Canada
Ages 18–70
Sunnybrook Health Sciences Centre · Sites in Canada
Ages 18+
A study can be open while its sites in Canada have not opened yet or have stopped. Only those recruiting at a site in Canada →
Of the 114 Depressive Disorder, Treatment-Resistant studies recruiting now, 26 (23%) set no upper age limit and 76 (67%) stop at 75 or younger; 1 takes children under 18; 13 take healthy volunteers.
This study: 25 Years to 65 Years · all sexes · healthy volunteers too.
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76 studies; the count open now beside each. This study's row is marked.
A study in two phases is counted once above. Listed by phase, each with its combined phases: Phase 1 5 · Phase 2 18 · Phase 3 12 · Phase 4 7
First in 2002; this study’s year is marked. 11 started in 2025.
By drug class, each counting the studies that test any of its medicines:
This study's planned enrollment of 45 is below the median of 80 across 49 observational studies indexed under Depressive Disorder, Treatment-Resistant.
Median enrollment 50 across the 70 interventional studies, 63 across the 6 observational. Of the 33 that completed or were terminated, 8 (24%) have results posted.
This tab as a report to print or save as PDF → With an account.
9 of 76 have an industry lead sponsor. The 10 most frequent:
Unity Health Toronto is the lead sponsor of 447 studies on the registry; 81 are open to participants now.
Of its 5 completed or terminated interventional studies of FDA-regulated products, 1 (20%) have results posted.
Unity Health Toronto has 7 studies filed under Depressive Disorder, Treatment-Resistant — fewer than ten, so there is no comparison to draw.
12 of the studies in Depressive Disorder, Treatment-Resistant with a site in Canada that are under way reach primary completion within a year, 1 of them phase 3. Phase 3 first, then by date:
| Study | Primary completion |
|---|---|
| NCT07262008Phase 3Women's College HospitalSustained Mood Improvement With Laughing Gas Exposure | 2027-02-01 |
| NCT05570344University of AlbertarTMS With and Without Text4Support for the Treatment of Resistant Depression. | 2026-12-31 |
| NCT06163625Unity Health TorontoThe Impact of Working Memory and Reward Markers on DLPFC Activity in Treatment-resistant Depression | 2026-12-31 |
| NCT06731621Centre for Addiction and Mental HealthPsilocybin for Treatment-Resistant Depression in Autism | 2027-01 |
| NCT07212465Rotman Research Institute at BaycrestAccelerated Neuromodulation of Anterior Cingulate Cortex for Depression | 2027-01-01 |
Add all 12 to your calendar (.ics) → With an account.
Among the 76 studies in Depressive Disorder, Treatment-Resistant with a site in Canada, from their registry updates:
This tab as a report to print or save as PDF → With an account.
The purpose of this study is to better understand how certain brain systems work in people with depression, especially in those whose symptoms have not improved with antidepressant treatments. The investigators are particularly interested in synaptic density, which helps to understand how different parts of the brain communicate with one another. Synaptic density levels have implications on overall brain function and cognition. By comparing brain function in people with treatment-resistant depression, people with treatment-responsive depression, and healthy controls, investigators hope to better understand why some individuals do not respond to antidepressants. This research may help guide the development of more effective treatments in the future.
This research project examines synaptic density in the brain. Synaptic density refers to the number of communication connections that exist between brain cells in a given area, which provides researchers with information about how efficiently brain regions communicate. Researchers are studying synaptic density to better understand how brain communication may differ in people with depression.
It is estimated that 30% of individuals with Major depressive Disorder (MDD) fail to respond to conventional antidepressant medication. Treatment resistant depression (TRD) patients also are more likely to have other psychiatric and medical diagnoses, poorer quality of life, and increased suicidal ideation. There are few treatment strategies available to target TRD and there is not a lot of evidence about how TRD differs from depression that responds to treatment.
In this study, the investigators will collect detailed information about participants psychiatric history and depression symptoms, as well as two brain scans using positron emission tomography (PET) and magnetic resonance imaging (MRI). PET imaging uses a radioactive agent (also called a tracer) to obtain pictures of the brain. The tracer used is called [18F]- SynVesT-1, which measures synaptic density. In addition, the MRI scan will be used to examine brain function when performing tasks involved in memory and learning about rewards. The ultimate goal of this study is to better understand synaptic density in the brain and how it relates to brain function during memory and reward learning tasks. This information will be important for advancing knowledge of the brain biology of TRD and potential new areas for treatment development.
Participants will be recruited from clinics at St. Michael's Hospital and the Centre for Addiction and Mental Health as well as from research programs at the two sites, which have ongoing MDD clinical trials where patients are required to be unmedicated prior to initiating treatment.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Key inclusion criteria for the MDD patients:
Key inclusion criteria for the Healthy Controls:
Exclusion Criteria:
Key exclusion criteria for the MDD patients:
Key exclusion criteria for the Healthy Controls:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The American Psychiatric Association’s manual of mental health diagnoses. DSM-5 (2013, revised as DSM-5-TR in 2022) replaced DSM-IV, and some studies still name the older edition. “Meets DSM criteria for …” means diagnosed by that edition’s diagnostic criteria, usually by a clinician in an interview.
DSM diagnostic criteria
The American Psychiatric Association’s manual of mental health diagnoses. DSM-5 (2013, revised as DSM-5-TR in 2022) replaced DSM-IV, and some studies still name the older edition. “Meets DSM criteria for …” means diagnosed by that edition’s diagnostic criteria, usually by a clinician in an interview.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Unmedicated Individuals with Treatment Resistant Depression
Diagnostic Test: PET scans
Unmedicated Individuals with Major Depressive Disorder
Diagnostic Test: PET scans
healthy controls with no previous psychiatric disorders
Diagnostic Test: PET scans
PET scans and PHNO scans
Synaptic Density
Synaptic density represents a promising biomarker for TRD, as it provides a direct index of neural circuit integrity and synaptic architecture (Appelbaum et al, 2022; Serano et al, 2022). Interventions shown to be effective in treatment-resistant populations, including rapid-acting antidepressants and neuromodulatory approaches, have been proposed to engage in synaptic plasticity-related mechanisms (Duman et al, 2016). As such, synaptic density measured using SV2A PET may offer insight into circuit-level abnormalities relevant to depression severity and treatment resistance, therefore offering a mechanistically informed approach for characterizing the biological correlates of TRD and supports its use in PET-based investigations of this population
Time frame: 3 years
Plan to share: Undecided
No publications or documents are linked to this record.
Started Aug 2025 (actual). Primary completion is estimated for Dec 2028, 40 months after the start.
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Depressive Disorder, Treatment-Resistant →