Inclusion Criteria:

• provide voluntary written informed consent for trial participation after the scope and nature of the investigation have been explained to them, and before starting any trial related activities
• be able to speak, read, understand, respond to questions and follow instructions in English
• have a DSM-IV severe depressive episode with psychotic features, as diagnosed by the MINI for single or recurrent episodes
• have a score on PANSS item "Delusions" AND/OR "Hallucinatory behavior" of at least 4 at screening and baseline
• have a PANSS Positive Scale score of at least 16 at screening and baseline
• have a total score of at least 18 on teh HAMD 17 item scale at Screening and Baseline
• be on a stable dose of usual treatment which has to consist of an anti-depressant, an antipsychotic, a mood stabilizer or any combination of these three drug classes
• be 18 up to and including 70 years of age at Screening
• must be willing to be hospitalized for at least 11 days from Screening onwards.

Exclusion Criteria:

• have any other psychiatric diagnosis except MDD
• have a lifetime psychiatric diagnosis of Bipolar Disorder I, schizophrenia or schizoaffective disorders
• are at significant risk of committing suicide
• are currently treated with carbamazepine or valproate
• are currently treated with midazolam
• have been treated with electroconvulsive therapy in the current episode
• are currently treated with more than one antidepressant
• are currently treated with more than one antipsychotic
• are currently treated with more than one mood stabilizer
• have usual treatment started or discontinued in the two weeks before randomization
• have a usual treatment dose change within the week prior to randomization
• have any clinically unstable or uncontrollable renal, hepatic, respiratory, haematological, cardiovascular or cerebrovascular disease that would put the patient at risk of safety or bias assessment efficacy
• have known hypersensitivity reactions to glucocorticoid antagonists
• have any clinically significant abnormal laboratory data
• have any untreated or uncompensated clinically significant endocrine disorder
• have a diagnosis or alcohol and/or drug dependence
• have a confirmed positive result on the drug screening test for any illicit drug except cannabis
• are using hormone replacement therapy at Screening
• require concomitant treatment with corticosteroids
• are subjects diagnosed with Cushing disease
• are women of childbearing potential without adequate contraception
• are women with a positive pregnancy test at screening or baseline or are breastfeeding mothers
• are male subjects with current diagnosis of prostrate hypertrophia or past history of symptoms of prostrate hypertrophia.