Adjuvant Treatment With a Glycine Uptake Inhibitor in Participants With Negative Symptoms of Schizophrenia (P05695) (MK-8435-001)

Inclusion Criteria: * Is diagnosed with non-first episode schizophrenia meeting Diagnostic and Statistical Manual (Version IV) criteria * Is receiving stable treatment with one of the following SGA: aripiprazole, olanzapine, quetiapine, risperidone, or ziprasidone * Is in the non-acute phase of illness and clinically stable for 3 months prior to study start as demonstrated by: treatment with current SGA or at least 12 weeks prior to study start; no increase in the level of psychiatric care due to worsening symptoms for at least 12 weeks prior to study start; and no dose change of SGA or change in medication to treat the symptoms of schizophrenia for 4 weeks prior to study start * Has a score ≥4 on 3 or more of the following Positive and Negative Symptoms Scale (PANSS) negative subscale items at study start: blunted affect, emotional withdrawal, poor rapport, passive social withdrawal, lack of spontaneity, motor retardation, and active social avoidance * Has an overall PANSS negative subscale score \> 20 Exclusion Criteria: * Has an overall PANSS positive subscale score ≥20 * Has a score ≥5 on 2 or more of the following PANSS positive subscale items at study start: delusions, hallucinatory behavior, excitement, grandiosity, or suspiciousness/persecution * Has a score ≥9 on the modified InterSePT Scale for Suicidal Thinking * Has a score ≥9 on the Calgary Depression Scale for Schizophrenia * Has a score ≥3 on the clinical global impression of Parkinsonism of the abbreviated …