Identifying Biological Markers for Severe Depression

Inclusion criteria for depressed patients: 1. Diagnostic and Statistical Manual of Mental Disorders 4th Edition (DSM-IV) diagnosis of Unipolar Major Depressive Disorder with or without psychotic features. 2. 21-item Hamilton Depression Rating Scale (HDRS) score greater than or equal to 21. 3. Thase Core Endogenomorphic Scale score greater than or equal to 8 on the items included in the 21-item HDRS. 4. Between 18 - 70 years of age. 5. If currently taking antipsychotic, antidepressant, anticonvulsant, and/or mood-stabilizing medications, must be stable on the medication for at least one-week prior to entering the study. 6. Pre-existing (current) primary treating psychiatrist for subjects with psychotic features. 7. Any secondary diagnoses from the anxiety disorder spectrum is acceptable. Primary pre-existing chronic Obsessive-Compulsive Disorder (OCD) will be an exclusion criteria. Inclusion criteria for healthy controls: 1. Between 18 - 70 years of age. 2. Have a HAM-D score of less than or equal to 5. Exclusion Criteria for depressed patients: 1. Electroconvulsive Therapy (ECT) in the 6 months prior to the study. 2. Abuse of drugs or alcohol in the 6 months prior to study. 3. Unstable or untreated hypertension or cardiovascular disease. 4. Use of additional prescription medications, street drugs, or alcohol during the week before the study. 5. Any Axis II diagnosis or traits which would make participation in the study difficult. 6. Current pregnancy or lactation. 7. Post-partum depression 8. Diagnosis of obsessive-compulsive disorder 9. History of significant cognitive decline Exclusion criteria for healthy controls: 1. Personal history of Axis I or Axis II disorders. 2. Active unstable medical problems. 3. Abuse of drugs or alcohol in the 6 months prior to study. 4. Use of additional prescription medications, street drugs, or alcohol during the week before the study. 5. Currently pregnant or lactating. 6. History of significant cognitive decline