Can DNA testing tell you about your health risks?

Can gene scans tell me about my risk of mental illnesses?

New tests that scan all of a person’s genes — that person’s “genome” — or large parts of his or her genome are now on the market.

From The National Institute of Mental Health (NIMH) 

Anyone who can afford the new scans can buy one, without a prescription or a health professional’s advice, by mailing a saliva sample to a company that sells the scans. Advertisements suggest that the company then can provide information about clients’ risks of developing specific diseases, based on variations found in their genes. [Editor’s note: Actions by the Food & Drug Administration currently do not permit these companies to interpret health-related data.]

It’s too early for these new genome scans to give people a complete picture of their risk of mental illnesses or to diagnose them. Scientists don’t yet know all of the gene variations that contribute to mental illnesses, and those that are known, so far, raise the risk by very small amounts.

23andMe Chips dna testingGenetic research might make it possible — one day — to provide a more complete picture of a person’s risk of getting a particular kind of mental illness or to diagnose it, based on his or her genes. That day isn’t here yet, although studies are underway now.

In the meantime, it’s important to know the difference between the new genome scans being advertised today and the kinds of traditional genetic tests doctors have been ordering for many years. Traditional genetic tests look for specific variations clearly shown by research to be the cause of certain rare diseases, such as cystic fibrosis, that generally are caused by variations in a single gene.

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Doctors order traditional genetic testing for people they think are at high risk of one of these rare diseases; for example, if the neurological disorder Huntington’s disease runs in a person’s family. The results enable patients and their doctors to make health-care decisions together.

But people who buy the new genome scans may not have any reason, such as family history, to suspect they’re at risk of one of these rare diseases. They may just want to randomly look at all of their genes with the hope of finding out if they’re at risk of any diseases.

As noted, when it comes to common diseases, like mental illness or adult-onset diabetes, not enough is known about which gene variations are involved to give a complete picture of a person’s risk.

Also, the genetics of mental illnesses and other common diseases are much more complex than the genetics of many of the rare, single-gene diseases. Mental illnesses appear to involve variations in many genes combined with other factors, such as stress.

People who are thinking about buying one of the new genome scans, to look at all or most of their genes with the hope of finding out if they’re at risk of a mental illness or another common disease, may want to get their health-care providers’ advice before taking that step.

People who suspect they have a rare disease strongly tied to their genetic make-up – for example, if a rare disease runs in their family – may want to ask their health-care providers about genetic testing. Their providers can tell them whether or not the disease can be detected through genetic testing at this time and, if so, what kind of test and follow-up care are needed.

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The company tells the client what gene variations he or she has, and offers to analyze the results or to allow the client to analyze the results on an interactive website.

Can the new genome scans tell me what diseases I might get?

To date, no gene variants are known that can predict with certainty whether or not someone will get a number of common diseases, including mental illnesses.

Scientists haven’t yet discovered whether many of the gene variations that occur in humans are connected to specific diseases or how much they raise or lower the risk.

For example, a genome scan might show that a person has one or more gene variations related to a common disease, such as adult-onset diabetes. But it’s likely that many other gene variations also contribute to this disease, and it’s not yet known which ones. The variations associated with most common diseases, to date, raise the risk only very slightly and, by themselves, don’t yet provide medically useful information.

An example using heart disease suggests how the results of the new genome scans might confuse consumers. Early research might have shown that certain gene variations are associated with a common kind of heart disease. People whose scans showed they didn’t have these variations might think they weren’t at risk.

They might think it would be safer for them than for other people to forego some of the healthiest, heart-protecting habits known to science: exercising, not smoking, and avoiding obesity. But it’s likely that, as with mental illnesses, this kind of heart disease involves many variations in many genes, and scientists don’t yet know what all of them are.

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Foregoing healthy lifestyle changes based on this incomplete genetic picture could contribute to illness that might have been prevented.

What can research about gene variations tell us about disease risk?

As they continue to discover combinations of gene variations and external factors that contribute to specific diseases, scientists are building a more complete picture of how to detect which people are at risk of common diseases.

This research also is helping to reveal the biological pathways through which gene variations contribute to disease. Scientists can use this information to design better screening and prevention for specific diseases, and find more precise molecular targets at which to aim as they develop new medications.

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