This single center, randomized, single dose, open-label, four period cross-over study will evaluate the relative bioavailability of RO4917838 and the effect of food following oral administration in healthy volunteers. Subjects will receive in randomized order single oral doses of RO4917838 film coated tablets, either in the fasted or fed condition, or RO4917838 hard gelatin capsules or RO4917838 oral suspension, with a washout period of at least 21 days between treatments. Anticipated time on study will be up to 23 weeks.

Inclusion Criteria:

• Healthy male and female volunteers, 18 to 65 years of age, inclusive
• Body mass index (BMI) 18 to 30 kg/m2 inclusive
• Healthy as determined by the Investigator on the basis of medical and surgical history and a complete physical examination
• Non-smoker or smoker of fewer than 10 cigarettes per day; subject must be able to refrain from smoking during the in-patient stays
• Females who are not postmenopausal or surgically sterile must agree to use two adequate methods of contraception as defined by protocol during the treatment period and for at least one month after the last dose of study drug

Exclusion Criteria:

• Any condition or disease detected during the medical interview/physical examination that would render the subject unsuitable for the study, place the subject at undue risk or interfere with the ability of the subject to complete the study in the opinion of the Investigator
• History of alcoholism, drug abuse and/or drug addiction within the last year prior to Period 1. Day -1 of the study
• History of any significant cardiovascular, hepatic, renal, respiratory, gastrointestinal, endocrine, immunologic, allergic, dermatologic, hematologic, neurologic, psychiatric disease, or cancer
• Any history of depressive episodes or treatment with antidepressants
• Any significant allergic reactions against any drug, or multiple allergies in the judgement of the Investigator
• Pregnant or lactating females
• Positive for hepatitis B, hepatitis C or HIV infection
• Participation in another investigational study of any type within 90 days of RO4917838 administration or within 6 times the elimination half-life of the tested drug, whichever is longer