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Like pneumonia, which can be caused by various bacteria, viruses, or chemicals, schizophrenia probably has multiple causes, all of which affect the brain in related ways. Research suggests that both genes and environmental factors are involved in developing schizophrenia. While 1 out of every 100 people has schizophrenia, having a biological relative with schizophrenia increases a person’s risk of developing this disorder. A person who has a genetically identical twin with schizophrenia has a 50% chance of having schizophrenia. A person with a sibling or a parent with schizophrenia has a 10% chance of having schizophrenia. Research is aimed at finding both the genetic factors that may put a person at increased risk for schizophrenia, and the environmental factors that may be involved. There is active and exciting research to find the genes that increase risk for schizophrenia. Three areas on various chromosomes have been linked to schizophrenia in more than one study; however, the actual gene that increases risk for schizophrenia has not yet been found.

The search for possible environmental factors is in very early stages. One prominent theory is that schizophrenia results from altered brain development before birth. For example, several, but not all, studies have shown that individuals who were fetuses during influenza epidemics are at increased risk of schizophrenia. A few studies have shown that individuals whose mothers endured severe starvation during pregnancy are at increased risk for schizophrenia. During fetal life the brain is actively developing. The theory is that these stressors somehow interfere with brain development.

In autopsy studies, the brains of individuals with schizophrenia have been examined. Here, several researchers have found that the organization of brain cells was more random than in the brains from mentally healthy individuals. In addition, they have found “nests” of brain cells in patients with schizophrenia in the mesolimbic areas of the brain, suggesting that these cells were somehow stopped in their programmed migration to their final resting place.

These and other studies hold promise for our eventual understanding of how genes and environment may interact to cause schizophrenia. Regardless, evidence is overwhelming that schizophrenia is a biologically based illness and that the previous view that parents or families cause schizophrenia is totally without merit.