A psychiatric disease characterized by a distorted interpretation of reality resulting in hallucinations, delusions, and disordered thinking and behavior. Contrary to belief it does not mean a split personality. Untreated, the disease can cause severe emotional, behavioral, health, and legal and financial problems. Lifelong treatment is needed, and can enable many patients to live normal productive lives. This is a serious mental disorder with about 10% of patients committing suicide. The disease usually first appears in the teenage years.