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Risk Factors for Schizophrenia

Learn about the risk factors that make people more susceptible to developing schizophrenia from psychiatrist Jeanie Tse in this Howcast video.


Schizophrenia is a disorder of brain development and our research tells us there is a genetic basis to schizophrenia. So, what we know is if you have an identical twin who has schizophrenia then your chances of developing schizophrenia are 50 percent, so half and half. If you have a first-degree relative, your parent or a non-identical sibling who has schizophrenia, then your risk is 10 percent.

So, we know that it's an increased risk above the general population risk if you have a family member. That's why we know it's genetic. We don't know quite which genes are involved yet. It's probably multiple genes, but we have a few genes that we're specifically focusing on with research to know whether they're involved in developing schizophrenia and how we might address that.

So, genes are one thing, but what we know, too, are the things that affect brain development will affect your risk of developing schizophrenia. So, the perinatal period, the pregnancy period and just after pregnancy and delivery period, is really an important time of risk for the fetus or baby to develop the risk for schizophrenia.

So, having low birth weight or bleeding during pregnancy has been associated with the onset of schizophrenia, or the risk for schizophrenia. In addition, exposure to viruses or toxins or malnutrition during pregnancy appear to be risk factors as well. So, those probably affect the development of the brain and lead to the onset of schizophrenia some 20 or 30 years later.

There's also a relationship between traumatic and stressful experiences- abuse and hardships in a person's life - that lead to the onset of schizophrenia. As well, substance use, in particular marijuana use, among people who have a genetic risk for schizophrenia has been implicated in leading to an increased risk.

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