Schizophrenia is a serious disorder which affects how a person thinks, feels and acts. Someone with schizophrenia may have difficulty distinguishing between what is real and what is imaginary; may be unresponsive or withdrawn; and may have difficulty expressing normal emotions in social situations.
Contrary to public perception, schizophrenia is not split personality or multiple personality. The vast majority of people with schizophrenia are not violent and do not pose a danger to others. Schizophrenia is not caused by childhood experiences, poor parenting or lack of willpower, nor are the symptoms identical for each person.
What Causes Schizophrenia?
The cause of schizophrenia is still unclear. Some theories about the cause of this disease include: genetics (heredity), biology (abnormalities in the brain’s chemistry or structure); and/or possible viral infections and immune disorders.
Genetics (Heredity)
Scientists recognize that the disorder tends to run in families and that a person inherits a tendency to develop the disease. Similar to some other genetically-related illnesses, schizophrenia may appear when the body undergoes hormonal and physical changes (like those that occur during puberty in the teen and young adult years) or after dealing with highly stressful situations.
Biology
Chemistry - Scientists believe that people with schizophrenia have an imbalance of the brain chemicals or neurotransmitters: dopamine, glutamate and serotonin. These neurotransmitters allow nerve cells in the brain to send messages to each other. The imbalance of these chemicals affects the way a person’s brain reacts to stimuli--which explains why a person with schizophrenia may be overwhelmed by sensory information (loud music or bright lights) which other people can easily handle. This problem in processing different sounds, sights, smells and tastes can also lead to hallucinations or delusions.
http://www.mentalhealthamerica.net/conditions/schizophrenia