The Effect of Quetiapine XR in Depressive Patients Showing Aberrant N100 Amplitude Slope

Recently, there are increasing data about intensity dependent amplitude change (IDAP: N100 amplitude slope) of auditory evoked Event Related Potential (ERP) components for its role on surrogate marker of central serotonergic activity. A high N100 amplitude slope reflects low serotonergic neurotransmission and vice versa. There are a couple of studies reporting associations of N1 amplitude slope with response to Citalopram (positive correlation) and Reboxetine (negative correlation) treatment in major depressive disorder patients (2,3). The investigator also published a case series about SSRI super-sensitivity and SSRI induced mania in patients with aberrantly high N100 slope (4). And serotonin transporter gene polymorphism was studied for its role about pathophysiology of bipolar disorder (5, 6, 7). Serotonin promoter gene was known to have significant relationship with N100 amplitude slope (8). Furthermore previous study showed that N100 amplitude slope was well correlated with hypomanic and hyperthymic personality (9). Conclusively from above results, the investigator hypothesized that if depressive patients show aberrant high or low N100 amplitude slope (N100 response outliers), they will not response well to SSRI medication. They will response better to quetiapine XR adjunctive therapy. In this study, the investigator will confirm it by comparing treatment effect between SSRI monotherapy and quetiapine XR adjunctive in aberrant N100 responder. Hypothesis First visit depressive patients might have monopolar or bipolar depression. If depressive patients show aberrantly high or low N100 amplitude slope, they will not response to SSRI medication. Patients who have aberrantly high or low N100 amplitude slope will response better to quetiapine XR adjunctive therapy.