A Safety, Efficacy and Biomarker Study of JNJ-42847922 in Participants With Major Depressive Disorder

This will be a multi-center (when more than one hospital works on a medical research study), randomized (study medication assigned to participants by chance), double-blind (neither the researchers nor the participants know what treatment the participant is receiving) and placebo-controlled (an inactive substance; a pretend treatment \[with no drug in it\] that is compared in a clinical trial with a drug to test if the drug has a real effect) study. This study will consist of an eligibility screening examination (between 28 days and 1 day prior to the first dose administration), a parallel group treatment phase of 10 days or 4 weeks, and a follow-up period of 2 weeks including 2 follow-up visits. The duration of study will be 12 months. Participants will be randomly assigned to receive either JNJ-42847922, Diphenhydramine or Placebo. Participants' safety will be monitored throughout the study.