Bipolar Disorder And Heredity

Bipolar disorder runs in families. More than two-thirds of those diagnosed with bipolar disorder have at least one close relative with bipolar disorder or clinical depression. Children who have a parent with bipolar disorder have a 25% chance of developing the disorder. Children born to two parents with bipolar disorder have a 72-75% chance of developing bipolar disorder. This shows that bipolar disorder has a genetic component. Part of the reason that children of bipolar disorder parents develop bipolar disorder could be environmental instead of genetic. The chronic family stress of having a parent in the emotional turmoil of bipolar disorder can increase the child’s chance of developing a mood disorder, whether or not they have a genetic tendency to do so.

If a person has the disorder, an identical twin to that person has a 70% likelihood of having the disorder as well. Fraternal twins have a 23% concordance rate. This means that if one fraternal twin has bipolar disorder, the other twin has a 23% chance of developing bipolar disorder. These incidence rates are not always what is shown by studies. Recent studies have shown rates of around 40% for identical twins and less than 10% for fraternal twins.

Research has failed to pinpoint a single gene as the precise cause of bipolar disorder. Scientific studies seeking to identify the genetic cause of bipolar disorder indicate that the disorder is likely caused from multiple genes. Scientists are continuing their search for these genes by analyzing genes from large samples of families affected by the illness. The researchers are hopeful that identification of the genes responsible for bipolar disorder will lead to the development of better treatments. It may also allow preventive interventions targeted at the underlying illness process to be developed.

In 2003, a group of American and Canadian researchers published a paper that used gene linkage techniques to identify a mutation in a specific gene as a possible cause of up to 10% of cases of bipolar disorder. This gene appears to be involved in dopamine metabolism, and may provide a possible target for new drugs for bipolar disorder. Dopamine is a neurotransmitter that has been implicated in several mental illnesses including schizophrenia.

Bipolar disorder is considered to be a result of complex interactions between genes and environment. Like many medical illnesses, the diatheses-stress model can be used to explain why some people develop bipolar disorder. The diatheses-stress model states that we are born with a prediposition to develop hereditary illnesses that run in our families. Environmental factors and stressors determine if we actually develop these disorders. So, though the potential to develop the illness is present at birth, our environment and lifestyle affect whether or not we develop the disorder.

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