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Heritability of Bipolar Disorder
Bipolar disorder is associated with imbalances of certain neurotransmitters in the brain and genes affecting the regulation of these neurotransmitters may play a big part in causing the development of the disorder. Research has shown that the various disorders on the bipolar spectrum have heritability factors between 0.7 and 0.8, indicating that genetic predisposition to bipolar disorder is perhaps the greatest significant factor which causes it and that genetic testing for bipolar disorder should be possible.
However, it is not the only factor – environmental, physical and social factors have also been implicated. A heritability of 1 would indicate purely genetic disposition but external factors ranging from lifestyle to stressful periods to biological events such as menopause can all come into play at the same time. Therefore, genetic testing can only be conducted with the caveat that it predicts those more at risk from bipolar disorder and not those who will definitely develop it.
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Genetic Predictors for Bipolar Disorder
A 2010 study in the American Journal of Medical Genetics isolated a set of 56 genes which appeared to strong indicators of the development of bipolar disorder. By comparing versions of these genes with the display of bipolar symptoms they were able to show a strong correlation between various genetic combinations and the development of the disorder.
However, the research also stressed that it was combinations of genes, rather than any single indicator, which served as predictors. There was no single overriding genetic factor that contributed to bipolar, rather a number of versions of genes that made it more likely. The more of these genes that a person had, the more likely they were to develop the disorder, but there was no absolute measure.
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Genetic Predictors for Bipolar Disorder
The progress in identifying the genes that contribute to bipolar disorder has led to the availability of blood tests which claim to be able to predict a patient's vulnerability. Psynomics became the first company to offer at home testing for the disorder in 2008. You simple deposit some saliva in a bag and send it back to them and they will mail you back the results.
However, such tests can be misleading. There is a long list of caveats; that a positive result only indicates that you have a predisposition to the disorder because of your genes, not that you have developed it; that a negative result does not rule it out because there may be other genes and environmental factors which could have led to the disorder.
Because of this, the test could be considered controversial; a positive or negative result is likely to play more to a particular patients neuroses than provide a definitive answer. A patient going through a stressful period who has a genetic predisposition to bipolar doesn't necessarily have bipolar, but a positive test could lead them to behave differently than if they didn't have the test at all. Because of the lack of certainty and the potential dangers of misdiagnosis, genetic tests still have a long way to go despite the increasing research indicating further linked genes.
Bipolar disorder is a mental health disorder with a strong heritability factor. There is a large group of genes which appear linked with the disorder and tests for these genes can help to predict those who are at risk. However, simply possessed a high risk factor does not necessarily mean that a patient has the disorder and many scientists believe that external, environmental factors also play a big part. Genetic tests can help to tell us who is more at risk but are unlikely ever to be 100% proof and as such should be treated with caution.
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Dr Deb, “At-home DNA Test for Bipolar Disorder”, http://drdeborahserani.blogspot.com/2008/03/at-home-dna-test-for-bipolar-disorder.html
Edvardsen, J. et al (2008) "Heritability of bipolar spectrum disorders. Unity or heterogeneity?" Journal of Affective Disorders 106
Medical News Today, “Researchers Refine DNA Testing For Predisposition To Bipolar Disorder” http://www.medicalnewstoday.com/articles/185012.php
Psynomics, “About Psynomics”, http://www.msnbc.msn.com/id/23337532/