A risk factor is something that increases your likelihood of getting a disease or condition.

It is possible to develop schizophrenia with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood is of developing schizophrenia. If you have a number of risk factors, ask your doctor what you can do to reduce your risk.

Family History

Schizophrenia has a genetic component. People who have a close relative with schizophrenia are more likely to develop the disorder. A monozygotic (identical) twin of a person with schizophrenia has the highest risk (40%-50%) of developing the illness. A child whose parent has schizophrenia has about a 10% chance. The risk of schizophrenia in the general population is only about 1%.

Brain Abnormalities

Many studies of people with schizophrenia have found abnormalities in:

    
  • Brain structure:     
  • Enlargement of the fluid-filled cavities, called the ventricles, in the interior of the brain
  • Decreased size of certain brain regions
  • Brain function: Decreased metabolic activity in certain brain regions
  • These abnormalities are quite subtle and are not typical of all people with schizophrenia. They do not occur only in people with this illness. Microscopic studies of brain tissue after death have also shown small changes in certain brain cells in people with schizophrenia. It appears that many (but probably not all) of these changes are present before a person becomes ill. Schizophrenia may be, in part, a disorder in brain development.

    Environmental Factors

    Schizophrenia is more common among people living in the city, those who live in the northern hemisphere, and those born during winter months.

    Complications During Pregnancy or Birth

    Complications during pregnancy or birth may increase an individual’s chances of developing schizophrenia later in life. However, none of the following complications have been proven conclusively:

        
  • Oxygen deprivation during pregnancy
  • Bleeding during pregnancy
  • Maternal malnutrition
  • Infections during pregnancy
  • Long labor
  • Prematurity
  • Low birth weight
  • Loss of Parent During Childhood

    Early parental loss, either from death or separation, may increase the risk for schizophrenia (as well as other psychiatric disorders).

    Socioeconomic and Cultural Factors

    Schizophrenia is much more common in lower socioeconomic classes. It may be a result of increased stress and poor nutrition. An alternative explanation is that people suffering from schizophrenia move downward to a lower social class.