Wikipedia, Schizophrenia: http://en.wikipedia.org/wiki/Schizophrenia

Schizophrenia, from the Greek roots schizein (σχίζειν, “to split”) and phrēn, phren- (φρήν, φρεν-, “mind”), is a psychiatric diagnosis that describes a mental illness characterized by impairments in the perception or expression of reality, most commonly manifesting as auditory hallucinations, paranoid or bizarre delusions or disorganized speech and thinking in the context of significant social or occupational dysfunction. Onset of symptoms typically occurs in young adulthood,[1] with approximately 0.4–0.6%[2][3] of the population affected. Diagnosis is based on the patient’s self-reported experiences and observed behavior. No laboratory test for schizophrenia exists.[4]

The disorder is primarily thought to affect cognition, but it also usually contributes to chronic problems with behavior and emotion. People diagnosed with schizophrenia are likely to be diagnosed with comorbid conditions, including clinical depression and anxiety disorders; the lifetime prevalence of substance abuse is typically around 40%. Social problems, such as long-term unemployment, poverty and homelessness, are common and life expectancy is decreased; the average life expectancy of people with the disorder is 10 to 12 years less than those without, owing to increased physical health problems and a high suicide rate.[6]