Neural Mechanisms of Intermittent Theta Burst Stimulation in the Core Depression Network

This study is looking at how a type of brain stimulation called intermittent theta burst stimulation (iTBS) — a non-invasive treatment that uses magnetic pulses to stimulate specific brain areas — works to relieve treatment-resistant depression. The goal is to better understand how it changes brain activity. **You may be eligible if...** - You are between 18 and 55 years old - You have a confirmed diagnosis of major depressive disorder (MDD) - You have tried at least 1 but no more than 7 antidepressant medications at adequate doses without improvement - You are not currently in an acute medical crisis **You may NOT be eligible if...** - You have metal implants in your head or body that are not MRI-safe - You have a history of seizures or epilepsy - You are currently pregnant - You have a neurological disorder affecting the brain - You have a serious or unstable medical condition Talk to your doctor to see if this trial is right for you.