The purpose of this study is to identify genes involved in depression. Specifically, the investigators will analyze some genes that may be related to whether or not a person responds to antidepressant medication. This project is part of basic scientific research to increase understanding of the role of genetic influences in psychological and mental processes involved in the response to treatment for depression.

Inclusion Criteria:

• History of Unipolar Major Depression
• Control subjects must be healthy normal adults

Exclusion Criteria:

• Subjects with mood symptoms that are not severe enough to qualify for MDD
• Subjects with any active medical illness that may be related to ongoing mood disorder
• Normal subjects must be free from: a psychiatric diagnosis, substance abuse, a history of seizure disorder, and any serious medical illness

Patients will be recruited from previous studies conducted at the Laboratory of Brain, Behavior, and Pharmacology, where subjects' response to treatment has already been determined. This strategy offers the advantage that no new subjects need to be enrolled in placebo-controlled treatment studies.