Schizophrenia is a mental disorder characterized by abnormalities in perceiving reality such as auditory hallucinations, disorganized speech and thinking, and significant social dysfunction. It has been recognized for centuries in ancient cultures and was classified as a distinct disorder in 1887. Symptoms are divided into positive symptoms which distort normal functions like delusions and hallucinations, and negative symptoms which diminish normal functions such as reduced emotional expression. Causes include both genetic and environmental factors. Types of schizophrenia include paranoid, catatonic, residual, and schizoaffective disorder. Treatment involves medications which can have side effects as well as developing social skills and avoiding drug use and social isolation to help prevent the disorder.