Olanzapine may have some antidepressant properties and olanzapine monotherapy has been shown efficacy in bipolar depressive episodes in retrospective studies. However, there has been no prospective study about the monotherapy of olanzapine. The investigators conducted a randomized, placebo-controlled study to test the efficacy of olanzapine monotherapy for treatment of the depressed phase of bipolar disorder.

The study was designed as a double-blind randomized controlled trial, with research assessors and patients intended to be blind to the intervention status. The staff members performing the assessment were not involved in implementing any aspect of the intervention.68 patients were randomized to assigned 6 weeks by olanzapine or placebo. Medications were provided in double-blind fashion. The assessments include Montgomery-Asberg Depression Rating Scale, Young Mania Rating Scale, clinical Global Impressions-Severity of Illness scale, Clinical Global Impressions-Improvement scale, response and remission rates, and Treatment Emergent Symptom Scale.

Inclusion Criteria:

• Outpatients with clinical diagnosis of bipolarⅠdisorder
• MADRS total score ≥ 20
• CGI-S rating ≥ 4
• Normal results of physical examinations, laboratory and electrocardiogram tests
• Being taken care of by a guardians during the trial

Exclusion Criteria:

• Pregnant or lactating women
• YMRS total score ≥ 15
• Treatment with olanzapine within 3 months prior to study entry
• Retrospective history of poor antidepressive response to or intolerance of olanzapine
• Mental retardation
• Addictive disorder
• Diabetes mellitus
• Dyslipidaemia
• Cardiovascular diseases
• Hypertension