DefinitionSchizophrenia is a mental disorder that makes it difficult to tell the difference between real and unreal experiences, to think logically, to have normal emotional responses, and to behave normally in social situations.Causes, incidence, and risk factorsSchizophrenia is a complex illness. Even experts in the field are not sure what causes it.Genetic factors appear to play a role. People who have family members with schizophrenia may be more likely to get the illness themselves.Some researchers believe that environmental events may trigger schizophrenia in people who are already genetically at risk for the disorder. For example, infection during development in the mother's womb or stressful psychological experiences may increase the risk for developing schizophrenia later in life.