Effect of Quetiapine on Sleep Architecture in Bipolar Depression and Major Depressive Disorder

Inclusion Criteria: 1. Provision of written informed consent; 2. A diagnosis of Bipolar Disorder Type 1,2 or NOS by Diagnostic and Statistical Manual of Mental Disorders- Fourth Edition (DSM-IV);OR Major Depressive Disorder 3. Males or Females aged 18 years or more; 4. Female patients of childbearing potential must be using a reliable method of contraception and have a negative urine human chorionic gonadotropin (HCG) test at enrolment; 5. Able to understand and comply with the requirements of the study; 6. Current depressive episode with a HAM-D17 score of 15 or more. Exclusion Criteria: 1. Current Manic, Hypomanic or Mixed episode, with YMRS 12 or more; 2. Current or past diagnosis of Schizophrenia; 3. Pregnant women, or women in childbearing age, not willing to use appropriate contraception or women currently nursing; 4. Patient on antipsychotic medication; 5. Patients who, in the opinion of the investigator, pose an imminent risk of suicide or a danger to self or others; 6. Known intolerance or lack of response to quetiapine fumarate, as judged by the investigator; 7. Use of any of the following cytochrome P450 3A4 inhibitors in the 14 days preceding enrolment including but not limited to: ketoconazole, itraconazole, fluconazole, erythromycin, clarithromycin, troleandomycin, indinavir, nelfinavir, ritonavir, fluvoxamine and saquinavir; 8. Use of any of the following cytochrome P450 inducers in the 14 days preceding enrolment including but not limited to: phenytoin, carbamazepine, barbiturates, rifampin, St. John's Wort, and glucocorticoids; 9. Administration of a depot antipsychotic injection within one dosing interval (for the depot) before randomization; 10. Substance or alcohol dependence at enrolment (except dependence in full remission, and except for caffeine or nicotine dependence), as defined by DSM-IV criteria; 11. Opiates, amphetamine, barbiturate, cocaine, cannabis, or hallucinogen dependence by DSM-IV criteria within 4 weeks prior to enrolment; 12. Medical conditions that would affect absorption, distribution, metabolism, or excretion of study treatment; 13. Unstable or inadequately treated medical illness (e.g., diabetes, angina pectoris, hypertension) as judged by the investigator; 14. Involvement in the planning and conduct of the study; 15. Previous enrolment in the present study; 16. Participation in another drug trial within 4 weeks prior enrolment into this study or longer in accordance with local requirements; 17. If participant's liver function testing is rated 2 in the upper limits of normal. 18. Diagnosis of Dementia 19. Regular use of benzodiazepines unless at a stable dose for at least 12 weeks.