While only about 50% of patients respond to first treatment in major depressive disorder, 30-40% did not remit after continuous 1 year treatment. However, patients must remain on their prescribed medications for at least 4 weeks without knowing whether the particular antidepressant will be effective. Studies have suggested a number of predictors of treatment response, but varying degrees of success and nearly all with poor prognostic sensitivity and specificity. The investigators investigated clinical symptoms, demographic and stress state, personality and genetic polymorphisms in patients of major depressive disorder treated with sertraline and performed multivariate analysis to extract the predicting factors. Moreover, the investigators tried to visualize weight of variables and pathway one another.