Biomarker-Guided Antidepressant Selection

Depression is one of the leading causes of disability worldwide. Common treatments like antidepressant medications and talk therapy work well for some people, but many others do not improve, even after trying multiple treatments. This study will investigate two alternative treatment options for people whose depression has not responded to standard treatments: repetitive transcranial magnetic stimulation (rTMS), a non-invasive form of brain stimulation, and ketamine, a fast-acting medication. It can be difficult to decide between these interventions in clinical practice, and selecting between them often comes down to patient preference and trial and error. This study is working to optimize the selection approach: using biological and behavioral markers to match each person to identify biomarkers that may predict response to rTMS or ketamine. Investigators believe that differences in how individuals respond to rTMS versus ketamine are partly explained by differences in how their brains are organized, and that these differences can be measured and used to guide intervention decisions. This is an early-stage pilot study designed to test whether this biomarker-based approach is practical and acceptable to patients. Investigators will evaluate how well a combination of brain imaging and clinical data can predict, at the individual level, who is likely to respond to rTMS versus ketamine. The ultimate goal is to develop a reliable, scalable tool that helps clinicians make faster and more informed intervention decisions, reducing the time people with treatment-resistant depression spend searching for an antidepressant that works.