Mild Traumatic Brain Injury and Post-Traumatic Stress Disorder

Background: \- Some people who have a traumatic brain injury (TBI) recover completely. Others, however, develop post-traumatic stress disorder (PTSD), with anxiety and depression. Research suggests that levels of a brain chemical called GABA may differ in people with PTSD compared to those without PTSD. Researchers want to see if TBI can affect GABA in the brain and help develop PTSD. To look at the brain, researchers will use imaging studies with the chemical 11C-Flumazenil, which will help the scan show GABA levels in the brain. Objectives: \- To study the relationship between PTSD and TBI. Eligibility: The subjects will be recruited from the Walter Reed National Military Medical Center (WRNMMC). * Individuals between 18 and 50 years of age who have PTSD and/or had a mild TBI. * Healthy individuals between 18 and 50 years of age who have no history TBI and no history of PTSD. Design: * Participants will be screened with a physical exam and medical history. Urine and breath samples will also be collected. * Participants will have two imaging studies, on the same day if possible. The first will be a magnetic resonance imaging scan to look at the brain. The second will be a positron emission tomography scan with the study chemical to look at GABA pathways in the brain....