The purpose of this trial is to investigate the efficacy of risperidone as an adjunct to an antidepressant treatment in the acute management of suicidality during an episode of major depressive disorder.

Using a double blind, placebo-controlled design, subjects diagnosed with a current episode of major depressive disorder (defined by DSM-IV criteria and supported by the Mini International Neuropsychiatric Interview), severe with suicidality despite currently taking an antidepressant, will be enrolled in the eight-week study. The treatment will be initiated by randomizing patients to receive risperidone or placebo in addition to the antidepressant that the patient is already taking. The clinical efficacy will be evaluated after 4 days, weekly for 4 weeks, then every other week for 4 weeks with the efficacy measures. During the eight-week study, treatment with risperidone or placebo will continue at the highest effective dosage (up to 2 mg per day). The dose of the antidepressant will not be changed during the study.

Inclusion Criteria:

1. 19-60 years of age
2. Diagnosis of major depressive disorder, currently severe with suicidality
3. A total score of Montgomery-Asberg Depression Rating Scale (MADRS) =/> 25 with the suicide sub-score =/> 4
4. Currently is taking an antidepressant at a therapeutic dose for longer than 3 weeks
5. In good physical health

Exclusion Criteria:

1. Depression without suicidality
2. Presence of major psychiatric conditions other than major depressive disorder, such as bipolar disorder, schizophrenia, or anxiety disorders (except for generalized anxiety disorder)
3. Depressive symptoms induced by alcohol or substance abuse
4. Psychotic features which are predominant at the initial evaluation
5. Unstable major medical illness, such as cardiac disease or diabetes
6. Female subjects who are pregnant, breastfeeding, or, if of child-bearing potential, unwilling to use adequate birth control measures