Schizophrenia is a mental disorder characterized by abnormal social behavior and failure to understand reality. Common symptoms include false beliefs, unclear or confused thinking, hearing voices that others do not, reduced social engagement and emotional expression, and a lack of motivation. People with schizophrenia often have additional mental health problems such as anxiety, depressive, or substance-use disorders. Symptoms typically come on gradually, begin in young adulthood, and last a long time. The causes of schizophrenia include environmental and genetic factors.