A Study of 6(S)-5-MTHF Among Serotonin Reuptake Inhibitor(SSRI)-Resistant Outpatients With Major Depressive Disorder (MDD)

The study consists of 8 visits over a period of 8 weeks or 60 days. Eligible participants will be randomized to double-blind treatment with placebo or Deplin (6(S)-5-MTHF). Participants will have a greater than 50% chance of receiving active medication (Deplin) at some point in the 8 week study. At the end of the double-blind phase, both responders and non-responders who have completed the 8 week study will have the option of receiving free, open-label adjunctive treatment with either 7.5 mg or 15 mg of 6(S)-5-MTHF for 12 months. Subjects who agree to receive open-label treatment with 6(S)-5-MTHF for 12 months will be assessed every three (3) months until the end of the follow-up phase.