If a patient does have a sufficient infusion response, and s/he is not already taking an antidepressant, then s/he will receive 6-weeks antidepressant research treatment with Sertraline, Fluoxetine, Paroxetine, or Escitalopram, followed by open clinical treatment. However, if s/he is already taking an antidepressant, then s/he will receive open treatment. If s/he does not have a sufficient infusion response, then s/he will receive open treatment.