The purpose of this study is to determine safety & efficacy of SEROQUEL SR™ in the treatment of major depressive disorder compared to placebo & to evaluate quality of sleep, overall quality of life, and effect, if any, on anxiety and satisfaction PLEASE NOTE: Seroquel SR and Seroquel XR refer to the same formulation. The SR designation was changed to XR after consultation with FDA.

Inclusion Criteria:

• Documented clinical diagnosis according to the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision) meeting criteria 296.2x Major Depressive Disorder,
• Single Episode, or 296.3x Major Depressive Disorder,

Exclusion Criteria:

• Patients with a DSM-IV Axis I disorder other than MDD w/in 6 months of enrollment,
• Patients with a diagnosis of DSM-IV Axis II disorder which has a major impact on the patients current psychiatric status.
• Patients whose current episode of depression>12 months or <4 weeks from enrollment