Schizophrenia is a mental disorder characterized by abnormal behavior, strange speech, and a decreased ability to understand reality. Other symptoms include false beliefs, unclear or confused thinking, hearing voices that do not exist, reduced social engagement and emotional expression, and lack of motivation. People with schizophrenia often have additional mental health problems such as anxiety, depression, or substance-use disorders. Symptoms typically come on gradually, begin in young adulthood, and, in many cases, never resolve.
The causes of schizophrenia include environmental and genetic factors. Possible environmental factors include being raised in a city, cannabis use during adolescence, certain infections, the age of a person's parents, and poor nutrition during pregnancy. Genetic factors include a variety of common and rare genetic variants. Diagnosis is based on observed behavior, the person's reported experiences and reports of others familiar with the person. During diagnosis, a person's culture must also be taken into account. As of 2013, there is no objective test. Schizophrenia does not imply a "split personality" or dissociative identity disorder, conditions with which it is often confused in public perception.
The mainstay of treatment is antipsychotic medication, along with counselling, job training, and social rehabilitation. It is unclear whether typical or atypical antipsychotics are better. In those who do not improve with other antipsychotics, clozapine may be tried. In more serious situations 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.
About 0.3% to 0.7% of people are affected by schizophrenia during their lifetimes. In 2013, there were an estimated 23.6 million cases globally. Males are more often affected and on average experience more severe symptoms. About 20% of people eventually do well, and a few recover completely. About 50% have lifelong impairment. Social problems, such as long-term unemployment, poverty, and homelessness, are common. The average life expectancy of people with the disorder is 10–25 years less than that of the general population. This is the result of increased physical health problems and a higher suicide rate (about 5%). In 2015, an estimated 17,000 people worldwide died from behavior related to, or caused by, schizophrenia.