by Tami Port MS

Created on: August 13, 2009

Bipolar disorder results from a combination of factors; the interplay of genetics and environmental stressors. How much of a role does heredity have in the development of this mental illness?

Early research on the genetics of bipolar disorder relied on twin studies and examination of inheritance patterns among family members. Now that the human genome has been decoded, science is getting closer to identifying all of the specific genes involved in the development of this mood disorder.

* Inheritance Patterns of Bipolar Disorder *

Family studies of inheritance patterns, as well as twin and adoption studies of those with bipolar disorder have revealed that first-degree relatives of affected individuals have a higher risk of developing bipolar symptoms. Still, a child of a bipolar and a nonbipolar parent have less than a 15% chance of developing the disorder, although those odds may increase if there are others in the family who have a mood disorder.

Studies of identical twins have shown that if one twin is bipolar, the other has at least an 85% chance of developing the disorder. Twins certainly share many of the same environmental factors as well, both in utero and throughout childhood, but shared experience does not account for the extremely high likelihood that genetically predisposed twins will share the disorder.

So it is established that bipolar disorder tends to run in families. But now, with the human genome mapped, scientists are starting to pinpoint the actual genes that are linked to the disorder.

* Genetics of Bipolar Disorder *

Within the last few years, researchers have identified several genes that appear to be associated with the disorder. Because a number of genes are involved in development of bipolar illness, the inheritance patterns are not straightforward, as indicated by the fact that children of a bipolar parent have a relatively small risk of developing the disorder. All those who may have a genetic predisposition don't necessarily ever end up developing bipolar symptoms.

The involvement of several genes, suggests that a range of biochemical problems can occur in people who possess a genetic predisposition for bipolar disorder, and that perhaps, the specific type and number of genetic abnormalities contribute to how the disorder manifests in an individual.

Our understanding of genetic disorders has exploded since the completion of Human Genome Project (HGP) in 2003. This 13-year project was launched cooperatively by the U.S. Department of Energy

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