Schizophrenia is a severe mental illness, affecting an estimated one percent of the population, according to Thomas F. Oltmanns and Robert E. Emery, authors of the 2007 publication Abnormal Psychology. The disorder results in a range of psychotic symptoms, from auditory hallucinations to grandiose delusions. Patients may also suffer from apathy and a lack of emotional display. It may be difficult to understand the roots of such a complex disorder, but all of the following are thought to play a role in its causation.
Environmental vs. Biological Causes of Schizophrenia
Much of the research regarding schizophrenia operates under the belief that there is a genetic component to the illness. According to work done by Gottesman and Reilly in 2003, research clearly suggests that there is heritability to schizophrenia (as cited by Oltmanns and Emery.) A study published in 1991 by Irving Gottesman of the University of Virginia revealed that there is a 46 percent risk that a person will develop schizophrenia if both of his or her parents have the disorder; the risk drops to 17 percent of only one parent has schizophrenia, but there still seems to be a genetic link to the illness, according to family studies. It has also been found that an individual has a 48 percent chance of developing this disorder if an identical twin is affected.
Perhaps providing the greatest evidence that schizophrenia has a genetic component, adoption studies suggest that the increased prevalence of schizophrenia of among family members is not due to environmental factors.
In 1966, psychiatrist Leonard Heston of the University of Washington conducted an adoption study, examining a group of 49 adopted children who were born to schizophrenic mothers. The study revealed that the adopted children had a 16.6 percent chance of developing the disorder (as cited by Oltmanns and Emery.) This risk was almost identical to the risk associated with having a schizophrenic biological parent and being raised by him or her, indicating that genetic predisposition has a much greater impact than the environment in which an individual lives.
Birth Complications and the Development of Schizophrenia
According to Oltmanns and Emery, problems during pregnancy are associated with the development of schizophrenia later in life. Examples of complications include lengthy labor and the wrapping of the umbilical cord around the neck of the baby. Such complications are detrimental because they “impair circulation or otherwise reduce the availability of oxygen to developing brain regions,” according to Abnormal Psychology.
The mother’s diet during pregnancy can also produce complications, negatively impacting the baby’s nervous system as it develops. In 1996, Susser et al. conducted a study of people conceived during the famine in the Netherlands, concluding that malnutrition led to twice the risk of schizophrenia (at cited by Oltmanns & Emery, 2007).
Other Factors Contributing to Schizophrenia
According to Oltmanns and Emery, a mother’s exposure to viral infections during pregnancy also had the potential to cause schizophrenia, as it can interfere with the baby’s neurological development.
Brain scans have indicated that neurological defects may play a role in the development of schizophrenia as well. Several studies have shown that schizophrenics are likely to have enlarged lateral ventricles, which are cavities in the brain filled with cerebrospinal fluid, according to Abnormal Psychology. Research also suggests that schizophrenics tend to have less brain tissue than the general population.
Decreased levels of brain tissue, combined with in utero viral infections, birth complications, and biological predispositions, seem to play a contributing role in the development of schizophrenia. Perhaps these multiple factors work together to cause the mental illness, or they may each contribute to the disease on their own.
Sources:
Gottesman, I. (1991). Schizophrenia Genesis: The origins of Madness. New York: Freeman.
Oltmanns, T., & Emery, R. (2007). Abnormal Psychology. New Jersey: Prentice Hall.
Jennifer Long - Jennifer Long holds a bachelor's degree in psychology from the Ohio State University and has completed research projects in the field.
