To assess the efficacy of acute treatment with 10 mg/day vortioxetine versus placebo on cognitive performance (focusing on the aspect concerning speed of processing, executive functioning, attention) in working patients with major depressive disorder (MDD).

Inclusion Criteria:

• The patient has MDD, diagnosed according to Diagnostic and Statistical Manual of Mental Disorders, 4th edition, Text Revision (DSM-IV-TR™) recurrent major depressive disorder (MDD) (classification 296.3x).
• The patient has a MADRS total score ≥26.
• The patient has had the current major depressive episode (MDE) for ≥3 months.
• The patient is aged ≥18 and ≤65 years.
• The patient is employed full or part-time (defined as minimum 50% full time working hours per week). Part time work should not be due to a medical or mental illness other than MDD.
• The patient has been in the current job/position for at least 3 months.
• The patient has no plans to change jobs or retire within treatment period.
• The patient is not on a sick leave, and at the Screening and Randomisation Visits, there are no plans to send the patient on a sick leave.
• The patient is not receiving disability benefits.

Exclusion criteria:

• The patient has a score ≥70 on the DSST (number of correct symbols) at the Baseline Visit.
• The patient is, in the opinion of the investigator, not able to complete the neuropsychological tests validly at the Baseline Visit.
• The patient has physical, cognitive, or language impairment of such severity as to adversely affect the validity of the data derived from the neuropsychological tests.
• The patient is diagnosed with reading disability (dyslexia).
• The patient has a history of lack of response to previous adequate treatment with vortioxetine or paroxetine.
• The patient has any current psychiatric disorder or Axis I disorder (according to DSM-IV-TR™ criteria) other than MDD, as assessed using MINI.
• The patient has a current or has had a diagnosis of dysthymic disorder within 3 months preceding the onset of current episode (DSM-IV-TR™ criteria).
• The patient has borderline, schizotypal, schizoid, paranoid, or histrionic, antisocial personality disorders (axis II) as comorbid or primary diagnosis (DSM-IV-TR™ criteria).
• The patient suffers from personality disorders, mental retardation, pervasive development disorder, attention-deficit/hyperactivity disorder, organic mental disorders, or mental disorders due to a general medical condition (DSM-IV-TR™ criteria).
• The patient has a current diagnosis or history of manic or hypomanic episode, schizophrenia or any other psychotic disorder, including major depression with psychotic features (DSM-IV-TR™ criteria).

Other protocol-defined inclusion and exclusion criteria may apply.