Is schizophrenia genetic?


As with many mental health disorders, the causes of schizophrenia are complex and not yet fully understood. What we do know indicates that an interaction between genetic and environmental factors is what determines whether someone will develop schizophrenia.


There is no question that genes play a role in schizophrenia. People with a close relative who is schizophrenic (such as a parent or sibling) are at an increased risk of developing the disease themselves--a 10% risk compared to the 1% found in the general population. Those with slightly more distant relatives (an aunt, uncle, grandparent, or cousin) are also at an increased risk. The greatest risk is for those who have an identical twin diagnosed with schizophrenia--their risk of developing the disease is around 50%.

There appear to be several genes associated with schizophrenia, with no one gene responsible for causing the disease. While some diseases can be screened for using genetic tests, there are so many gene variations thought to contribute to schizophrenia that a genetic test for the disease is unlikely.


As noted above, someone with an identical twin who is schizophrenic has about a 50% chance of developing schizophrenia. If genes were the only determining factor, one would expect this risk to the undiagnosed twin to be 100%. In addition, more than half of schizophrenics do not have any family members with the disorder. These facts suggest that genes make a person susceptible to schizophrenia, and environmental factors trigger the disorder. This interaction, between genes and environment, seems to be necessary for schizophrenia to develop.

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