Investigating the Muscarinic System in Schizophrenia Using Positron Emission Tomography

This study is composed of two participant groups. 1) Antipsychotic-free patients with schizophrenia and 2) healthy matched controls. The healthy controls will be matched as closely as possible for age, sex, cannabis, and nicotine consumption to the patient group. All participants will undergo a positron emission tomography (PET) scan to measure the M4R binding with \[11C\]MK-6884 and examine its relationship with clinical and cognitive measures. Participants who meet the inclusion and exclusion criteria at screening visit (visit 1) will be enrolled into the study. All participants will undergo a PET scan with the novel tracer \[11C\]MK-6884 to examine its binding with M4R. The third visit will consist of a MRI scan and cognitive assessments. Participants with schizophrenia will have visit four, which occurs 6 weeks after the first antipsychotic trial, initiated by their treating physician. If the treating physician starts a second antipsychotic trial, then a visit five occurs 6 weeks after the second trial. Both visits four and five involve clinical and cognitive assessments.