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Schizophrenia: Overview and Risk Factors

Schizophrenia is a disease marked by abnormal thoughts and/or hallucinations, as well as disorganized speech and behavior. It affects about 1 percent of people worldwide.

Researchers believe that schizophrenia is in part caused by elevated levels of dopamine in the brain, but there are probably many other factors that are responsible for the disease.

Risk Factors

  • Age: The disease generally develops before age 25.
  • Genetics: Genetic factors are thought to play a role, although no specific gene has been identified, and several genes may play a role. Approximately half of monozygotic (identical) twins are affected when the other twin has schizophrenia. The increased risk to dizygotic (fraternal) twins is around 15 percent, and first-degree relatives have about a 10 percent risk.
  • Environmental exposures: Some investigators believe that certain early exposures are associated with a risk for schizophrenia. Fetal malnutrition, paternal age over 50 years, and births that occur during winter or spring are associated with increased risk. Children who were not breast-fed for at least two weeks have been shown to have increased risk of schizophrenia.
  • Infection: Infection with the parasite Toxoplasma may affect the central nervous system and may be associated with schizophrenia.
Schizophrenia: Diagnosis and Treatment >>