The Impact of Working Memory and Reward Markers on DLPFC Activity in Treatment-resistant Depression

Major Depressive Disorder (MDD) is a very common illness that is usually treated with antidepressant medication. Depression can be caused by many things such as childhood experiences, genetics, and changes in the way the body and brain function. For those with depression where medication and psychotherapy have limited benefit, repetitive transcranial magnetic stimulation (rTMS) is an effective treatment. rTMS is a treatment that involves stimulating certain areas of the brain with magnetic field pulses. Over time, the magnetic field pulses can gradually change the activity level of the stimulated brain region. This can be helpful in treating some kinds of psychiatric and neurological disorder, including MDD. It is not fully known how rTMS changes brain activity to improve symptoms of depression. However, certain brain areas responsible for behaviours impacted by depression are underactive in those with depression. One of those brain regions called the dorsolateral prefrontal cortex (DLPFC), and the investigators will target this region using rTMS. By increasing the activity of these regions, rTMS could potentially improve depression symptoms. For participants receiving rTMS, the investigators will be using the participant's brain scan to better understand brain activity of the brain region stimulated by rTMS before and after treatment. In this study, the investigators will be collecting detailed information about participants' psychiatric history and depression symptoms, as well as brain scans and saliva samples. The saliva samples will undergo proteomic (having to do with proteins) analyses to identify biological markers ("biomarkers": biological features (e.g.: gene, protein) that can be measured to indicate factors related to rTMS response. The investigators' goal is to use this information to help us understand whether improvement to rTMS depends on brain activity or proteomic factors localized to two specific behaviours impacted by depression: reward processing and working memory (the capacity to hold information temporarily, such as holding a person's address in mind while listening to instructions about how to get there).

NCT Number	NCT06163625
Lead Sponsor	Unity Health Toronto
Conditions	Major Depressive Disorder, Treatment Resistant Depression
Enrollment	50 participants
Start Date	2025-01
Primary Completion	2026-12-31 (estimated)
Study Completion	2026-12-31 (estimated)
Updated on ClinicalTrials.gov	2024-12-19