The Causes of Schizophrenia
While an exact cause of schizophrenia is still unknown, researchers do know that the brains of people living with schizophrenia are different from those undiagnosed with the illness. It is too early to classify schizophrenia as either a neurodevelopmental (impairment of the growth and development of the brain) or a neurodegenerative (progressive loss of structure or function of neurons) disorder, as both seem to occur over the course of the illness. Research strongly suggests the emergence of schizophrenia is a result of both genetic and environmental factors.
Genetics
Unlike other genetic conditions such as Huntington's or cystic fibrosis, it is believed that no one single gene causes the disease by itself but rather that several genes are associated with an increased risk of schizophrenia. While schizophrenia occurs in one percent of the general population, having a history of family psychosis greatly http://archpsyc.ama-assn.org/cgi/content/abstract/65/1/28. Schizophrenia occurs at roughly ten percent of people who have a first-degree relative with the disorder, i.e., a parent or sibling. However, the highest risk occurs when an identical twin is diagnosed with schizophrenia. The unaffected twin has a roughly 50 percent chance of developing the disorder.
The genetic component appears to extend beyond family environment. For example, children with a parent living with schizophrenia who were put up for early adoption still develop schizophrenia at a higher rate than the rest of the of the population.