• Change from Baseline to Week 8 on the total score of the clinician rated
  
• 17-Item Hamilton Depression Rating Scale (HAM-D17)
  

• The rating of the Clinical Global Impression Improvement (CGI-I) and the Clinical Global Impression Severity (CGI-S) scales at Week 8
  
• Proportion of patients who demonstrate clinical improvement at Week 8, where improvement is defined by a score of 1 or 2 on the CGI-I scale
  
• Proportion of patients who achieve remission at Week 8, where remission is defined by a total score of < or = 7 on the HAM-D17
  
• Change from Baseline on the Hospital Anxiety and Depression (HAD) total score and the Depression and Anxiety Subscale scores at Week 8
  

Inclusion Criteria:

• Male and female adults, 18 through 70 years of age, inclusive
• Diagnosis of Major Depressive Disorder, single or recurrent episode, according to DSM-IV criteria
• HAM-D17 total score > or = 22 at Screening and Baseline
• CGI-Severity score > or = 4 at Screening and Baseline
• Only patients who complete the core protocol are eligible to participate in the Open-Label Extension Phase

Exclusion Criteria:

• History of bipolar disorder (I or II), schizophrenia, schizoaffective disorder, eating disorder, or obsessive compulsive disorder
• Any current Axis I disorder other than major depressive disorder which is the focus of treatment
• Substance or alcohol abuse in the last 30 days, dependence in the last 6 months
• Concomitant psychotropic medication, including herbal preparations and melatonin
• Psychotherapy of any type
• Female patients of childbearing potential who are not using effective contraception

Other protocol-defined inclusion/exclusion criteria may apply