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Genetic testing for bipolar disorder

"Dear Sarah, where do I go to get genetic testing for bipolar disorder?"

This is one of the most common questions I get asked and it is time to explain clearly that THERE IS NO GENETIC TEST for bipolar.

There is no reliable testing for genetic testing for bipolar disorder.

The confusion on this issue has lately been made worse by charlatans who claim to have a test - for a (steep) price.

It has been known for some time now that bipolar has a hereditary, and therefore a genetic, component.

Progress on DNA Testing for Bipolar Disorder

Although the chance of an individual having bipolar disorder is around 2%, this rises to 10% - 20% if one parent is bipolar, and 40% if both parents have bipolar disorder.

(These estimates vary and different researchers have come up with different numbers. Some put the risk as high as 70% if both sides of the family have a strong pattern of bipolar disorder across several generations.)

So why no genetic test for bipolar?

Genetic Test for Bipolar Raises Concerns

Genetic testing for bipolar disorder doesn't address the 20-30% contributed by other factors.

Although over a dozen genes have been "implicated" or "associated" with bipolar, there is not yet conclusive scientific evidence of a definitive bipolar gene. It has simply not been proven that any single gene or cluster of genes clearly indicates the presence of bipolar disorder, or even the high probability that an individual with these genes will have the disorder.

Twin studies (studies of identical twins) suggest that bipolar disorder will never be detectable through genetic testing. Even though there is such strong tendency for the illness to run in families, the twin studies have shown that there is only approximately 57% of cases of bipolar in an identical twins. In 43% one twin will have the disorder while their twin does not.

(Other studies of identical twins have come up with other percentages. The numbers may differ but the principle is the same - identical twins do not always both develop bipolar, showing it genes alone are not an explanation.)

Do we really want genetic testing for bipolar disorder?

This is significant because if bipolar was a completely genetic illness, 100% of the time, both of the twins would have the illness as identical twins share identical genes.

Currently experts believe that genetic factors account for around 70% - 80% the the causes of bipolar disorder. The Genetics of Bipolar Disorder

University of Miami researchers suggest a complex mode of inheritance, similar to that seen in diseases like diabetes and hypertension. In this model there are multiple genes involved, rather just one dominant gene. That is, there are multiple susceptibility genes, and the risk of developing manic-depressive illness probably increases when an individual has more or most of these genes.

Some of the implicated genes are found on chromosomes 4, 6, 12, 13, 15, 18, 21 and 22.

Ethics of bipolar and genetic tests

Genetic testing for bipolar disorder raises ethical, legal, and practical issues.

Even if genetic testing for bipolar disorder was reliable and available, there may be reasons why it may not be widely used.

Some fear that such testing would be used by employers and colleges and may lead to unwarranted discrimination.

Others argue that as genes are NEVER COMPLETELY determinative of bipolar disorder, such a "bipolar test" would not really progress us beyond the current situation where we must focus on the symptoms of bipolar disorder.

Interestingly, research has already begun into whether people with disorder would use such a test to help decide whether or not to conceive a child or to terminate a pregnancy.

In one study, 35% self-reported that they would likely be influenced by such testing to choose to not have children. This sentiment was strongly tied to perceived stigma against people with the illness.

However, another study found that if genetic fetal testing for bipolar became available the majority of people would want to run the test, but an overwhelming majority said they they would NOT abort.

This kind of research into possible attitudes based on a hypothetical, currently non-existent bipolar test is probably of limited use. Until real genetic testing for bipolar disorder is available and a better understanding of the 20% - 30% of non-genetic factors that cause bipolar are understood, it is simply too speculative.

More on Attitudes to a Genetic Test for Bipolar

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