Major depressive disorder (MDD) remains amongst the leading causes of disability in Canada and worldwide, and the COVID-19 pandemic has exacerbated this situation. The high prevalence and disability associated with MDD make research aimed at understanding its pathophysiology and developing effective treatments an important priority for public health.
Over the last decade, repetitive transcranial magnetic stimulation (rTMS), a form of non-invasive brain stimulation, has become a first-line treatment option for depressed patients, especially for those with MDD that have not responded adequately to antidepressant therapies. However, efforts to develop and optimize novel antidepressant treatments for MDD and treatment-resistant depression (TRD) have been challenging, primarily because our understanding of depression pathophysiology and antidepressant mechanisms is still in its early stages.
A team from the Department of Psychiatry of the University of British Columbia (UBC) conducted a clinical trial to investigate the treatment effect of a 4-week course of rTMS therapy on patients with TRD. They recruited 52 patients for the trial, and of those, 38 (26 female; average age 42) agreed to participate in a separate inquiry involving a single rTMS session inside an MRI scanner that generated functional MRI images of brain activity in real-time. Specifically, during the first single rTMS session, the team used the functional MRI images to measure neuroplastic changes in brain connectivity induced by the rTMS. They then assessed the association between these neuroplastic changes and the improvement in depressive symptoms observed after the 4-week rTMS treatment.
The researchers reported their results in the American Journal of Psychiatry, and this work was highlighted in the Brain & Behavior Research Foundation. The study found that rTMS stimulation of the right dorsolateral prefrontal cortex led to significant acute changes in functional connectivity, which were positively correlated with clinical outcomes after a 4-week course of rTMS treatment. Specifically, TRD patients who exhibited the most significant changes in brain connectivity during the initial rTMS session were more likely to experience greater benefits from the subsequent 4-week treatment course. These results suggest that evaluating changes in brain connectivity following the initial rTMS session may help to identify individuals who are more likely to respond positively to a full course of rTMS treatment.
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