Patients in level 3 will be randomly assigned to one of the following 4 groups: 1) Either Paroxetine combined with Lamotrigine or Paroxetine combined with Bupropion if they resist two antidepressants including Paroxetine. 2) Either Escitalopram combined with Mirtazapine or Escitalopram combined with Aripiprazole if they resist two antidepressants including Escitalopram. 3) Patients who does not respond to both Paroxetine and Escitalopram will be randomly assigned to either 1) or 2).