The purpose of this study is to evaluate the safety and efficacy of escitalopram to an active comparator in severely depressed patients

Escitalopram is the S-enantiomer of citalopram. Both escitalopram and citalopram are selective serotonin reuptake inhibitors (SSRIs) and are used to treat depression in adults. This study is designed to evaluate the safety and efficacy of escitalopram and an active comparator in severely depressed patients.

Inclusion Criteria:

• Patients must meet DSM-IV criteria for Major Depressive Disorder.
• Patients must have severe depression.
• MADRS greater than or equal to 30

Exclusion Criteria:

• Women who are pregnant, women who will be breastfeeding during the study, and women of childbearing potential who are not practicing a reliable method of birth control.
• Patients who are considered a suicide risk.
• Patients who currently meet DSM-IV criteria for: a principal diagnosis for Axis I disorder other than MDD (comorbid GAD is allowed), bipolar disorder, schizophrenia or any psychotic disorder, obsessive-compulsive disorder, dysthymia.
• Patients with a family history of bipolar disorder, schizophrenia, or any psychotic disorder.
• Patients with history of any psychotic disorder or any psychotic feature.