Olanzapine Compared to Lamotrigine in the Prevention of Depressive Episode in the Patients With Bipolar Disorder

Background: Bipolar disorder is a highly recurrent disease and has great impact on the function of patients. Depressive symptoms consist of more than 50% of life time during the illness and may lead to self harm or suicidal behaviors. Lamotrigine, a kind of mood stabilizer, was proved to be effective in preventing depressive episode in Bipolar disorder. However, it is still lacking evidence that monotherapy with atypical antipsychotics such as olanzapine had the efficacy of preventing the recurrence of depressive episode in the patients with bipolar disorder although it had demonstrated good prevention in manic episode of bipolar disorder. Methods: The investigators will enroll 60 patients who had bipolar disorder in remission state for at least two months and have already received olanzapine or lamotrigine as the maintenance treatment. The patients maintained with olanzapine will be applied to olanzapine group (N=30) whereas those maintained on lamotrigine will be applied to lamotrigine group (N=30) for one month before entering into this study. They will be followed up to 12 months. The demography data will be compared between two groups. The concomitant medicine in the maintenance period of the subjects recruited will be recorded and analyzed. The time period to recurrence of depressive episode will be compared between groups. In addition, they will investigate if there is any independent factor such as comorbid substance use disorder, alcohol use disorder, personality disorders, other psychiatric disorders (posttraumatic stress disorder, eating disorder), or medical illness correlating with higher recurrent rate of depressive episode in bipolar disorder.