Objective: Statins, or 3-hydroxyl-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, which are potent inhibitors of cholesterol synthesis, are widely used in the treatment of hypercholesterolaemia and prevention of coronary artery diseases. Evidence from clinical trials also show other beneficial actions of statins unrelated to their cholesterol lowering effects. In experimental animal studies, it was reported that simvastatin, a statin agent, may alter dopaminergic and glutamatergic functions. Dopaminergic overactivity and dysfunction of glutamatergic transmission is associated with the pathogenesis of schizophrenia. This study aims to examine the chronical effects of simvastatin on experimental psychosis models in mice.