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What causes schizophrenia?

Donna Hill Howes, RN
Family Medicine
Although no one knows the exact cause, or causes, of schizophrenia, research shows that it is probably a combination of two main factors: your genes and your environment. Studies show that genes play a major role in schizophrenia because it runs in families. For example, if you are the identical twin of someone with schizophrenia, you have a much higher chance of developing the disease yourself.

However, not all identical twins have schizophrenia, which suggests that genetic makeup is not enough to cause this disease. Scientists think that the genes you inherit may interact with environmental factors. This combination of genes and environment may be what triggers the disease. Some environmental factors that may increase the risk for schizophrenia include exposure to viruses while still in the womb, and the use of psychoactive drugs (such as cocaine, alcohol, ecstasy, or marijuana) as a teenager.

Scientists are also looking at the link between schizophrenia and the balance of certain chemicals, called neurotransmitters, in the brain. It may be that people with schizophrenia have an imbalance of neurotransmitters, especially the chemicals dopamine and glutamate. However, more research needs to be done before the cause of schizophrenia can be really understood.
Dr. Michael Roizen, MD
Internal Medicine

Experts wish they could answer this question as decisively as a two-year-old tells you his name, but no one knows yet what specifically causes schizophrenia, or why some people get it and others do not. That being said, there are risk factors that can increase the likelihood that you will develop schizophrenia. For example, if a parent or sibling has schizophrenia or a delusional disorder, you have a higher risk. Research indicates that if your mother was malnourished, had a viral infection, or took certain types of medicines while she was pregnant with you, you may have a higher risk as well. Finally, researchers have theories that the brain’s messengers (neurotransmitters) do not work properly in people with schizophrenia, which may cause them to develop the disorder. Keep in mind, though, that just because you have a higher risk of developing schizophrenia does not guarantee you actually will.

There is no known single cause responsible for schizophrenia. It is believed that a chemical imbalance in the brain is an inherited factor which is necessary for schizophrenia to develop. However, it is likely that many factors--genetic, behavioral, and environmental--play a role in the development of this mental health condition.

Schizophrenia is considered to be multifactorially inherited. Multifactorial inheritance means that "many factors" are involved. The factors are usually both genetic and environmental, where a combination of genes from both parents, in addition to unknown environmental factors, produce the trait or condition. Often, one gender (either males or females) is affected more frequently than the other in multifactorial traits. There appears to be a different threshold of expression, which means that one gender is more likely to show the problem, over the other gender. Slightly more males develop schizophrenia in childhood, however, by adolescence schizophrenia affects males and females equally.

Although some people think schizophrenia is a result of circumstances that occurred during a person's childhood, this is not the case. Although siblings are more likely to acquire the disorder than others, this is the result of genetics. While doctors are not certain about the causes of schizophrenia, they do believe genetics plays a role. Another potential contributor is a birth defect. It is possible that a mother who has the flu during her second trimester or a complication that causes a lack of oxygen during birth will have a child with schizophrenia.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.