The main variable of interest will be the magnitude of activity within the amydala. For each patient, regions of interest (ROIs) will be drawn manually to encompass the amygdala within each hemisphere with the aid of each patient's anatomical images. Magnitude of activity with the ROIs will be recorded. A generalized linear mixed model will be used to analyze group data with treatment, and time of session (baseline, 1-week, 8-week) as factors into the analysis. As we expect that the sample size of patients with La/La genotype will be smaller in each treatment group, the primary analysis will be done only in MDD patients with S/Lg alleles to prove our hypothesis. To examine the association between changes in amygdala activity and response in depression severity the change in HAM-D for each patient over 8 weeks will be regressed on the corresponding change in amygdala activity. A similar approach will be used to correlate 1-week change in activity with 8-week change in depression severity. The other regions that are functionally or structurally connected with amygdala such as anterior cingulate region (ACC), dorso-lateral prefrontal cortex (DLPFC), dorso-medial prefrontal cortex (DMPFC), and precuneus (PCC) will also be selected for exploratory analysis