Recent studies show that 25 – 30% of depressed patients never fully recover, resulting in a treatment-resistant condition. Thus, depression is a major cause of human suffering. We are interested in finding new ways of identifying and alleviating treatment-resistant depression, and we believe that recent advances in brain imaging can contribute to achieving that goal. In this project, we will use a novel compound ([N-methyl-11C]mirtazapine) that we invented for examining the neurochemistry of brain receptors involved in antidepressant actions.