Risk factors for schizophrenia include the following:
- Abnormalities in brain structure
- Abnormal brain chemistry
- Birth trauma
- Seasonality (exposure to a virus)
- Environmental conditions
Genetic Factors & Schizophrenia Risk
Heredity is the most well established schizophrenia risk factor. People who have immediate family members with schizophrenia have a 10 percent chance of developing the disorder, ten times that of the general population.
Other personality disorders, including those with psychotic symptoms, also seem to be more prevalent in families with schizophrenia. Despite the chance for inheritance, the number of children born to parents with schizophrenia doubled in the first 50 years of the 20th century.
A recent study that seems to support a genetic cause of schizophrenia suggests that identical twins stand a 50 to 85 percent chance of sharing the disease. Furthermore, it shows this to be about three times that for fraternal twins. Still, most studies fail to identify the exact mechanism and location of genetic transmission, though they do identify possible genes and chromosomes.
Because not all identical twins share the disease, and because people without familial history develop it, it is likely that there are other physiological and environmental risk factors involved.
Brain Structure, Chemistry & Schizophrenia Risk
Computerized functional imaging of the brain has found decreased blood flow to the frontal lobes of people with schizophrenia. These types of brain abnormalities forecast certain symptoms, like loss of attention, difficulty with abstract thinking, and the inability to solve problems.
Birth Trauma & Schizophrenia Risk
Some evidence suggests that infants who experience birth trauma or complications while in the womb are at greater risk for schizophrenia. Maternal illness may play a part as well. A mother who contracts a virus like the flu, especially during her second trimester, may increase the risk for her child. It is not known, whether the virus itself or the immune response to it increases the risk.
Some studies have shown that winter birth may be associated with schizophrenia, especially during immune response and illness. Furthermore, viruses in the womb are more common during the winter months. This has led some researchers to consider intrauterine viral infection during the winter as a risk factor. The same link, however, is found for major mood disorders, like bipolar disorder.
Environmental Factors & Schizophrenia Risk
Environmental factors and stress are thought to trigger the onset of schizophrenia. For example, moving, troubled relationships, problems at work, or substance abuse may aggravate the constellation of risk factors and lead to psychosis.