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

The purpose of this study is to evaluate the safety and tolerability of JNJ-42847922 in participants with Major Depressive Disorder (MDD).

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.

Eligibility Criteria:
Inclusion Criteria:

* Before randomization, a woman must be either: 1) Not of childbearing potential: postmenopausal; permanently sterilized; or otherwise be incapable of pregnancy. 2) Of childbearing potential and practicing a highly effective method of birth control consistent with local regulations regarding the use of birth control methods for participants participating in clinical studies: example, established use of oral, injected or implanted hormonal methods of contraception; placement of an intrauterine device (IUD) or intrauterine system (IUS) in combination with barrier methods: condom with spermicidal foam/gel/film/cream/suppository or occlusive cap with spermicidal foam/gel/film/cream/suppository; male partner sterilization; true abstinence. Women must agree to continue using these methods of contraception throughout the study and for at least 3 months after receiving the last dose of study medication
* Participant Body mass index (BMI) must be between 18 and 30 kilogram per square meter (kg/m2) inclusive
* Participant must meet the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) or 5 diagnostic criteria for major depressive disorder (MDD) without psychotic features, and confirmed by the Mini International Neuropsychiatric Interview (MINI) 6.0; Participant must have an Inventory of Depressive Symptomatology- Clinician rated-30 (IDS-C30) total score greater than or equal to (\>=) 30; Participant is either currently antidepressant naive or currently being treated with a maximum of two concurrent antidepressants. If the subject is currently treated with antidepressants, they have to be given at an optimal dose and for at least 4 weeks, but not longer than 24 weeks with a suboptimal response
* A man who is sexually active with a woman of childbearing potential and has not had a vasectomy must agree to use a barrier method of birth control e.g., either condom with spermicidal foam/gel/film/cream/suppository or partner with occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam/gel/film/cream/suppository, and all men must also not donate sperm during the study and for 3 months after receiving the last dose of study drug
* Participant must be willing and able to adhere to the prohibitions and restrictions specified in this protocol

Exclusion Criteria:

* Women who is pregnant or breast feeding
* Participant has a history of malignancy within 5 years before screening (exceptions are squamous and basal cell carcinomas of the skin and carcinoma in situ of the cervix, or malignancy that in the opinion of the investigator, with concurrence with the sponsor's study responsible physician, is considered cured with minimal risk of recurrence)
* Participant has a primary DSM diagnosis of general anxiety disorder (GAD), panic disorder, obsessive compulsive disorder (OCD), posttraumatic stress disorder (PTSD), anorexia nervosa, or bulimia nervosa. Subjects with comorbid GAD, social anxiety disorder (SAD), or panic disorder for whom MDD is considered the primary diagnosis are not excluded
* Participant has a length of current major depressive episode (MDE) \>24 months despite adequate treatment
* Participant has failed more than 2 treatments with a different pharmacological mode of action despite an adequate dose and duration during a previous, or the current depressive episode