The purpose of the study is to evaluate the long-term efficacy and safety of Saredutant in patients with depression. The primary objective is to evaluate the efficacy and safety of Saredutant 100 mg once daily compared to placebo in the prevention of relapse of depressive symptoms in outpatients with major depressive disorder who achieved an initial response to 12 weeks of open-label treatment with Saredutant.

Inclusion Criteria:

• Diagnosis of major depressive disorder, as defined by Diagnostic and Statistical Manual of Mental Disorders 4th edition (DSM-IV) criteria and confirmed by the semi-structured Mini International Neuropsychiatric Interview (MINI), recurrent episode.

Exclusion Criteria:

• Total score of 28 or less on the Montgomery and Asberg Depression Rating Scale (MADRS).
• Clinical Global Impression (CGI) severity score of less than 4.
• Duration of the current depressive episode less than 2 months or greater than 2 years.
• Elderly patients with a Mini-Mental State Examination (MMSE) total score <25.
• Patients with a history or presence of bipolar disorders or psychotic disorders.
• Patients with alcohol dependence or abuse or substance dependence or abuse in the past 12 months except nicotine or caffeine dependence.
• Benzodiazepine or sedative-hypnotic use greater than 2 days per week during the month prior to entry into the Acute Phase.
• Patients who have used the following prior to entry into Acute Phase: antipsychotics within 3 months, fluoxetine within 1 month, Monoamine oxidase inhibitors (MAOIs) within 2 weeks, other antidepressant or mood-stabilizer (lithium, anticonvulsants) within 1 week.

The investigator will evaluate whether there are other reasons why a patient may not participate.