Schizophrenia is a mental disorder, sometimes called split personality disorder that makes it difficult to tell the difference between real and unreal experiences, to think logically, to have normal emotional responses in social situations. 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. Schizophrenia may have a variety of symptoms. Usually the illness develops slowly over months or years.