Schizophrenia is the name for any of a group of mental disorders characterized by abnormal thought, mood and behavior. For example: thought: misinterpretation of reality, frequently inclined towards self-protection from perceived harm mood: inappropriate emotional response, lack of empathy with others behavior: withdrawn, regressive, and bizarre The cause of schizophrenia is not known. More than 90% of schizophrenic conditions begin before the age of 50.