PET Imaging of mGLuR5 With Drug Challenge

Inclusion Criteria: * 18-65 years old * English speaking * No other Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) diagnosis present, besides required as below. Inclusion criteria for depressed subjects * clinical diagnosis of a current or past depressive episode * medication free for at least 2 weeks * Score \>16 on Hamilton Depression Rating Scale (HDRS) if currently depressed or \<11 if not currently depressed * treatment or non-treatment seeking who understand that this study is for research purposes only Inclusion criteria for healthy controls * no current, or history of, any DSM-IV diagnosis * no first-degree relative with history of psychotic, mood, or anxiety disorder Inclusion criteria for PTSD subjects * current Post-Traumatic Stress Disorder, as determined by the Structured Clinical Interview for DSM-IV-Text Revision (TR) (SCID) patient research edition * Clinician Administered PTSD Scale for DSM-IV-TR (CAPS) score of 50 or higher Inclusion criteria for trauma control subjects -history of trauma (meeting the criterion A of PTSD but not a full diagnosis of PTSD) Exclusion Criteria: * Current or past significant medical, neurological, or metabolic disorder or loss of consciousness for 5 minutes or more * active, significant suicidal ideation * implanted metallic devices or any Magnetic Resonance (MR) contraindications * women who are pregnant or breastfeeding * met DSM-IV criteria for alcohol/illicit substance dependence in their life-time or met alcohol/illicit substance abuse within past year * history of prior radiation exposure for research purposes within the past year such that participation in this study would place them over FDA limits for annual radiation exposure. This guideline is an effective dose of 5 rem received per year * blood donation within eight weeks of the start of the study * radiation exposure at work that precludes study participation * blood pressure \>140/80