Schizophrenia is a serious chronic mental disorder characterized by psychotic symptoms (such as hallucinations and delusions), rambling speech, impaired thinking, flat affect, and poor social functioning. The word "schizophrenia" means "split mind" and refers to the loss of reality that sometimes occurs. The onset of schizophrenia can be sudden (days, weeks, or months), but it usually develops slowly over the course of several years. Typically affecting about 1 percent of the general population, the peak onset in males is between the ages of 15 and 25; in females, between ages 25 and 35. Schizophrenia can be divided into five subtypes: catatonic, disorganized (also known as hebephrenic), paranoid, undifferentiated, and residual. Each type has its own set of characteristics, in addition to the general symptoms of schizophrenia.

About 25 percent of people with schizophrenia have a poor prognosis. They are unable to hold a job or live independently. Suicide attempts and episodes of depression are common during the course of the illness. Proper treatment and support enables 50 to 75 percent of people to be productive.