In Canada, 1 in 20 people live with depression. While many treatment options exist, a significant number of individuals do not respond adequately to current therapies, highlighting the urgent need for more effective solutions. One effective alternative to medication is theta burst stimulation (TBS). This technique uses magnetic fields applied to the outside of the head to modulate brain regions believed to be involved in depression. This treatment produces antidepressant effects in only three minutes per session—ten times faster than standard treatments.

Despite its growing use, we still do not fully understand how TBS improves symptoms of depression. In earlier work supported by Brain Canada, our team used advanced brain imaging to show that a single TBS session can rapidly change activity in brain networks linked to mood regulation.

In this new project, we will study how a full week of intensive TBS treatment (i.e., 6 daily sessions for a total of 30 sessions over 1 week) affects the brain’s ability to form new connections between nerve cells, a process known as neuroplasticity. Individuals with treatment-resistant depression will receive daily stimulation sessions and brain scans before and after treatment. We will also track changes in their symptoms to understand how improvements relate to brain recovery.

This pioneering study is the first to directly measure changes in brain connections following TBS. The findings will help explain how this treatment works, identify who is most likely to benefit, and guide future efforts to make depression care faster, more effective, and more personalized. Conducted at The Royal’s Neuromodulation Research Clinic, this project will also strengthen Canadian expertise in advanced brain imaging and innovative treatments for depression, helping translate scientific discoveries into routine treatments offered to Canadians.