This is a pilot project to study if repetitive Transcranial Magnetic Stimulation (rTMS) will benefit patients with bipolar depression safely. Based on published studies, this study hypothesizes that rTMS on the left dorsal prefrontal lobe will improve symptoms in some patients who have failed at least two medications.

Candidate with bipolar depression will be screened after signing informed consent. Those who meet the selection criteria will be treated with daily rTMS for 3 weeks and be followed-up at 2 weeks. Participants will keep their ongoing medication unless a medication significantly increases the possibility of seizure. They must be on the same dose of antidepressant medication for least 4 weeks without improvement of symptoms before being recruited into the study. Mood and other observed mental status will be measured by standard psychological scales.

Inclusion Criteria:

• bipolar I or II patients, currently in a depression episode
• Patient must have failed at least 2 medication
• Score of 21-item Hamilton Rating Scale for Depression (HAM-D)

Exclusion Criteria:

• Rapid cycling bipolar or mixed episode of mood disorder by definition of current DSM criteria
• Substantial risk of suicide during the screening period that requires inpatient care
• Presence of psychosis
• Dual diagnosis of other primary, currently clinically significant severe mental disorders
• History of other significant neurological diseases, such as seizure disorder, stroke, brain tumors, abnormalities in the blood vessels in brain, dementia, Parkinson's disease, Huntington's chorea or multiple sclerosis
• History of any medical event that may increase the risk of having seizure, such as head trauma with unconsciousness for more than 5 minutes or a family history of seizure
• Significant medical complications that may deteriorate during the trial or have increased likelihood of danger consequences
• Patients who are pregnant or intend to become pregnant during the study period
• Any metallic prosthesis in head, neck or upper body (including cardiac pace maker) that cannot be safely removed during treatment
• Current Vagus Nerve Stimulation (VNS) treatment or Electroconvulsive Therapy (ECT) treatment, or with history of failed ECT treatment
• Patient's Motor Threshold for TMS cannot be detected
• Significant side effects which are intolerable during the screening or any later stage of the trial
• Started psychotherapy within the previous 8 weeks or foreseeable psychotherapy will be started or changed in 6 weeks