Boston area men and women with MDD were recruited from 01/13/2014-11/11/2014 via Institutional Review Board (IRB)-approved newspaper, television, internet, and radio ads initiated by Massachusetts General Hospital (MGH) and Boston Clinical Trials (BCT). Screened and eligible patients returned one week later for a baseline visit and were randomized consecutively to double-blind treatment with placebo or LDN 1 mg b.i.d. The randomization list was generated by an online randomization program and maintained by the research pharmacist. Subjects were treated for 3 weeks, with weekly assessments. All subjects were required to continue on their baseline antidepressant regimen without changes for the duration of the study; they were likewise asked not to modify any other allowed baseline medications that they had been taking prior to entering the study. Adherence was determined by weekly pill counts; protocol violation was defined as less than 80% adherence.