Schizophrenia is a mental disorder characterized by a breakdown in thinking and poor emotional responses. Common symptoms include delusions, such as paranoia; hearing voices or noises that are not there; disorganized thinking; a lack of emotion and a lack of motivation. Schizophrenia causes significant social and work problems. Symptoms begin typically in young adulthood and about 0.3–0.7% of people are affected during their lifetime. Diagnosis is based on observed behaviour and the person's reported experiences. Genetics, early environment, psychological and social processes appear to be important contributory factors. Some recreational and prescription drugs appear to cause or worsen symptoms. The many possible combinations of symptoms have triggered debate about whether the diagnosis represents a single disorder or a number of separate syndromes. Despite the origin of the term from the Greek roots skhizein ("to split") and phrēn ("mind"), schizophrenia does not imply a "split personality", or "multiple personality disorder"—a condition with which it is often confused in public perception. Rather, the term means a "splitting of mental functions", reflecting the presentation of the illness.
The mainstay of treatment is antipsychotic medication, which primarily suppresses dopamine receptor activity. Therapy, job training and social rehabilitation are also important in treatment. In more serious cases—where there is risk to self or others—involuntary hospitalization may be necessary, although hospital stays are now shorter and less frequent than they once were. The disorder is thought to mainly affect the ability to think, but it also usually contributes to chronic problems with behaviour and emotion. People with schizophrenia are likely to have additional conditions, including major depression and anxiety disorders; the lifetime occurrence of substance use disorder is almost 50%. Social problems, such as long-term unemployment, poverty, and homelessness are common. The average life expectancy of people with the disorder is 12 to 15 years less than those without. This is the result of increased physical health problems and a higher suicide rate (about 5%).