Risk Factors of Who Gets Schizophrenia

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By studying the frequency of schizophrenia in various groups of people, using a science called epidemiology, scientists have uncovered a number of risk factors for developing schizophrenia. This information has provided clues to guide research into the causes of schizophrenia.

Taking all people into account, just less than 1% of the population (0.8% according to the (National Comorbidity Study) have schizophrenia. That amounts to approximately 2.2 million people in the United States alone.

Not everyone has the same risk of developing schizophrenia, however. By far the most significant risk factors for developing schizophrenia have to do with family members. This is the reason that scientists now believe that genetics are the most important factor in developing schizophrenia.

Family Risk Factors

  • Having a first degree relative such as a brother or sister with schizophrenia raises your risk of developing schizophrenia by about 10%. This is true even if your sibling is a fraternal (non-identical) twin.
  • Having one parent with schizophrenia raises your risk of schizophrenia by around 13%. This is true even among children who were subsequently adopted in childhood.
  • Having an identical twin with schizophrenia raises your risk to approximately 50%.
  • If both parents have schizophrenia your overall risk of developing schizophrenia is 36%.

Non-Family Risk Factors

Researchers have identified a number of different risk factors and risk-minimizing factors related to the frequency of schizophrenia among different groups of people. A couple of examples below:

  • Living in a densely populated city. People born or raised in dense urban areas are more likely to develop schizophrenia than people from the country.
  • Being African American was once considered a risk factor because African Americans are 1.5 times more likely than white Americans to develop schizophrenia. However, that effect is due to the greater numbers of African Americans living in cities and is not true when only people living in the country are considered.
  • Hispanic Americans may be less likely to develop schizophrenia. Hispanic residents of Los Angeles were half as likely to develop schizophrenia as non-Hispanic residents. However, this does not take into account that ethnically Hispanic people are of many racial groups, and so it isn't clear if the effect is one of culture or genetics.
  • Prenatal exposure to hunger. The children of women experiencing famine during the first three months of their pregnancy have been shown to be more likely to develop schizophrenia.

It is important to realize that these risk factors do not, in themselves, indicate a cause of schizophrenia. Instead, scientists are looking for underlying differences among these groups of people that can explain why they experience different levels of risk.

Stress and Schizophrenia

Stress is not believed to be a risk factor for developing schizophrenia, although that is a very commonly held mistaken belief people who come from abusive families or traumatic childhoods are not more likely to develop schizophrenia than those from healthy childhoods when other risk factors are taken into account.

Why do people believe that childhood stress causes schizophrenia? Having schizophrenic parents, or living in a crowded inner city, which are risk factors, often leads to a traumatic childhood. Also, during the prodromal stage of the illness, before full-blown symptoms develop, people’s lives tend to become very chaotic, with relationships disrupted, jobs lost. These events seem later to have contributed to the illness, but were actually signs of the illness coming on.

Many people with schizophrenia had clearly traumatic or abusive childhoods. These people suffer a compounded tragedy because they are less likely to have been able to develop resources and support systems that might help them cope with the illness. However, many people with schizophrenia came from healthy, loving, and supportive homes. It is unfair to blame these loving parents for the illness with which their children suffer. To do so only contributes to the stigma that tells people to be ashamed and afraid of the diagnosis of schizophrenia.

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Article Sources
  • National Comorbidity Survey. National Comorbidity Survey. Harvard School of Medicine, 2005.
  • Schizophrenia: a detailed booklet that describes symptoms, causes, and treatments, with information on getting help and coping. National Institutes of Mental Health. (2006). 

  • Torrey, E.F. Surviving Schizophrenia: a Manual for Families, Patients and Providers, 5th Edition. New York: HarperCollins Publishers, 2006.