Schizophrenia Schizophrenia is a mental disorder marked by the loss of contact with reality. When a person's thinking, feeling, and behavior is abnormal, it interferes with his or her ability to function in everyday life. Delusions, hallucinations, and irregular thinking and emotions are produced. If these signs are present, he or she may have the mental illness called schizophrenia. About one hundred years ago, schizophrenia was first recognized as a mental disorder and researchers have been searching for a cure ever since. The cause of schizophrenia is still unknown today and scientists have concluded that schizophrenia has more than one cause. Scientists have developed dozens of the