Characterizing Synaptic Density in Treatment Resistant Depression

This research project examines synaptic density in the brain. Synaptic density refers to the number of communication connections that exist between brain cells in a given area, which provides researchers with information about how efficiently brain regions communicate. Researchers are studying synaptic density to better understand how brain communication may differ in people with depression. It is estimated that 30% of individuals with Major depressive Disorder (MDD) fail to respond to conventional antidepressant medication. Treatment resistant depression (TRD) patients also are more likely to have other psychiatric and medical diagnoses, poorer quality of life, and increased suicidal ideation. There are few treatment strategies available to target TRD and there is not a lot of evidence about how TRD differs from depression that responds to treatment. In this study, the investigators will collect detailed information about participants psychiatric history and depression symptoms, as well as two brain scans using positron emission tomography (PET) and magnetic resonance imaging (MRI). PET imaging uses a radioactive agent (also called a tracer) to obtain pictures of the brain. The tracer used is called \[18F\]- SynVesT-1, which measures synaptic density. In addition, the MRI scan will be used to examine brain function when performing tasks involved in memory and learning about rewards. The ultimate goal of this study is to better understand synaptic density in the brain and how it relates to brain function during memory and reward learning tasks. This information will be important for advancing knowledge of the brain biology of TRD and potential new areas for treatment development.