Add-on Simvastatin in Schizophrenia Trial

Inclusion Criteria: * Age 18-70 years * Available for follow up during the study protocol * DSM-IV schizophrenia * Positive and Negative Syndrome Scale (PANSS) baseline score of ≥50 * Score of 3 or higher on the Severity of Illness scale of the Clinical Global Impression (CGI) * Not completely refractory to antipsychotics: evidence for at least partial responsiveness to antipsychotic medication * Evidence for current clinical stability * Capacity to provide informed consent * Provided informed consent * Patients taking concomitant, non-investigational medications that are not listed in Exclusion Criteria #1 * Patients speaking Spanish or English * Women using acceptable methods of birth control, including barrier method Exclusion Criteria: * Currently taking a statin OR any of the following: * Other lipid-lowering drug; * Anti-inflammatory drugs or aspirin; * Systemic antibiotic, anti-viral or anti-fungal drugs (within the past 4 weeks); * Potent inhibitors of the cytochrome P450 isoform 3A4 (CYP3A4); * Digoxin (Lanoxin®), nefazodone (Serzone®), niacin, cyclosporine (Neoral®, Sandimmune®), danazol, warfarin (Coumadin®), amiodarone, verapamil, Cordarone®, or Inderal®. * Patients with known hypersensitivity to simvastatin or any other statin drug * Active liver disease or unexplained persistent elevations of serum transaminases * Renal insufficiency * Serious or unstable medical condition that require close medical attention, such as cancer, unstable heart failure, uncontrolled hypertension/asthma/COPD * Current drug use disorder (abuse/dependence) * Pregnancy and lactation * Psychiatric disorders other than schizophrenia or schizoaffective disorder requiring pharmacotherapy * Suicidal or homicidal intent * Severe cognitive impairment that might compromise competency to sign informed consent or the validity of the cognitive outcome measure * Organic brain disorder, including epilepsy; mental retardation; or a medical condition whose pathology or treatment would likely alter the presentation or treatment of schizophrenia * Current participation in another clinical trial * Patients on more than 2 anti-psychotic medications (patients will not be tapered off effective medications for the purpose of participating in research) * LDL cholesterol \>100 mg/dL with known coronary hard disease. LDL cholesterol \>130 mg/dl with 2 or more of the following risk factors: smoking; hypertension; low HDL cholesterol (\<40 mg/dL); age \>45 years (men) or age \>55 years (women); family history of premature CHD (CHD in 1st degree relative male\<55; female \<65