Grant: CIHR Fellowship

Major depressive disorder is a leading cause of global disability, and approximately 30% of patients are resistant to conventional antidepressant pharmacotherapy. Intermittent theta burst stimulation is a non-pharmacological, non-invasive method for stimulating the brain. Stimulation of the left dorsolateral prefrontal cortex is cleared by the Food and Drug Administration and Health Canada for treatment resistant depression; it has well established antidepressant effects. New research has also shown that stimulation of the dorsomedial prefrontal cortex is also effective in treating depression. We predict that some patients will respond better to dorsomedial vs. left dorsolateral prefrontal cortex stimulation. The problem, however, is that there is no valid way of determining which brain region we should target for each individual patient. We therefore plan to use a type of brain scan called functional magnetic resonance imaging, in conjunction with patient's psychiatric symptom profiles, to give us information to make an informed decision on which brain region we should stimulate. To demonstrate our prediction we will test this prediction method on a sample of 348 patients with treatment resistant depression; including a minimum of 65% female participants. All participants will receive 30 sessions of intermittent theta burst stimulation, as well as functional magnetic resonance imaging before and after treatment. We will measure changes in depression before, during, and after treatment using validated depression questionnaires such as the Hamilton Depression Scale 17, Quick Inventory of Depressive Symptomology, and the Columbia Suicide Severity Rating Scale. We believe that patients will experience a greater reduction in depressive symptoms if we can individualize their brain stimulation to the correct brain regions. We also believe that patients will experience positive neurological restoration to brain regions that were previously abnormal due to their depression.