PET Imaging of Cyclooxygenase in Participants With Major Depressive Disorder (MDD)

Study Description: This study will examine whether cyclooxygenase 1 (COX-1) and cyclooxygenase-2 (COX-2) are detectable in the brain of individuals with major depressive disorder (MDD). Objectives: Primary Objective: To determine whether COX-1 and COX-2 are detectable in the brains of individuals with MDD experiencing a major depressive episode (MDE). Endpoints: Primary Endpoints: Group A - Calculation of COX-2 density from \[11C\]MC1 PET scans, using baseline scans and scans after blockade with celecoxib. Group B - Calculation of the density of COX-1 using \[11C\]PS13 Secondary Endpoints, common to both groups: 1. the relationship between peripheral markers of inflammation and COX binding; 2. the relationship between clinical rating scales and COX binding