Serum Markers as a Bioassay for Unipolar Depression

Inclusion Criteria (Depressed): * Aged 18 to 60. * Meets DSM-IV criteria for Unipolar Major Depression, either single or recurrent. * 21 item Hamilton Depression rating scale score greater than 18. * Capable of providing informed consent. * Has an established residence and phone number. Exclusion Criteria: * Meets DSM-IV criteria for Bipolar Disorder, Schizophrenia, Schizoaffective disorder or other major Axis I Psychiatric disorders (except for depression and phobia per above). * Addison's Disease, Cushing's Disease, or other known dysfunction of the HPA-cortisol axis. * Rheumatoid arthritis, lupus, or other condition associated with increased inflammation. * Regular use of non-steroidal anti-inflammatory medications, steroids, or other medications know to interact with the inflammatory process of the HPA axis. * A medical condition or regular use of a mediation, which I the opinion of the investigator is likely to influence the inflammatory or HPA responses. * Pregnancy. * Meets DSM-IV criteria for substance abuse or dependence in the last month. * Regular cigarette smoking. * History of fainting or other significant adverse event during blood drawing in the past.