- Lydia Ramsey/Business Insider
Ever considered getting a peek inside your genes?
Today, it seems easy. Find a personalized gene-testing service – there are more than a dozen companies in the US alone – spit in one of the tubes the company sends you, pop it in the mail, and check out your results online.
But how much can the average person learn from one of these tests?
In most cases, they can’t tell you whether you or your children will develop a specific disease — even breast cancer.
- Ethan Miller/Getty
Saying you have the gene “for” an illness typically means that one or both copies of a gene (you have two copies of each gene, one from each parent) has a mutation that’s been linked with that illness. But having a mutated gene does not necessarily mean you’ll develop that illness.
In 2013, Angelina Jolie wrote an article in the New York Times about her decision to have her breasts removed after she’d discovered she had a genetic mutation that dramatically raised her risk of developing breast cancer (she also had a family history of breast cancer). About 10% of all breast cancers in the US are linked to the mutation Jolie had. About 90% of all breast cancers are not.
In other words, having the mutation doesn’t necessarily mean you’ll get breast cancer, but it does mean that you’re significantly more likely to get it – especially if you also have a family history of it. And not having the mutation doesn’t mean you’re risk-free. In other words, “you could have the mutation and not get it, or you could not have the mutation and get it,” said Klitzman.
For psychological illnesses like depression or anxiety, the picture is even more blurry.
- Eka Shoniya/Flickr
Many of our observable traits – from aspects of our personality to the color of our eyes – cannot be narrowed down to one or two genes. This appears to be especially true for psychiatric characteristics like intelligence or illnesses like depression, said Klitzman. (A 2014 study he co-authored which was published the Journal of Genetic Counseling came to similar conclusions.)
“For things like intelligence there’s easily 100 different genes involved. So the notion that you’re going to test for a few of them and that’s going to be predictive, that’s not reflecting the complexity of genetics and of the mind and brain,” Klitzman said. A 2015 study published in the journal Nature Neuroscience was the first to identify two networks – each of which contain hundreds of genes – which appear to play a role in cognitive function.
In order for one of these tests to *really* predict your risk of disease, there are two major factors they’d have to account for: 1) your environment, and 2) your behavior.
- Scott Barbour/Getty Images
Genetics plays a big role in whether or not we develop certain diseases. But so does our environment and our behavior. Everything from what we eat to where we’re raised and how often we exercise can affect our risk of developing certain diseases.
“Research suggests that some 50% of all depression cases are linked with genetics. The other 50% is environment. So if you’re just looking at the genetic factors, you’re missing everything else,” said Klitzman.
Smoking, for example, dramatically raises your risk of developing lung cancer and heart disease; eating right can help lower your chances of developing stomach cancer and obesity.
There’s still a lot we don’t know about our genes.
The vast majority of personal genetics tests that are available today use something called SNPs, or single nucleotide polymorphisms, to test for genetic variants linked with certain traits. They’re the most common type of genetic variation among people, but they also represent only a tiny fraction of all of our DNA.
“Up until a few years ago we thought 98% of the genome was junk DNA, which turned out not to be quite true,” said Klitzman.
So while that science continues to develop, you might want to focus on the factors that you can control, like eating right and exercising.
There’s still no overarching, official system for evaluating any one of the thousands of available genetics tests out there.
- Lydia Ramsey/Business Insider
No evidence-based process for assessing personal genetic tests yet exists. Nevertheless, according to EGAPP, an CDC-backed initiative launched in 2004 to come up one such system, more than 1,000 genetics tests are available today.
The organization’s working group has published a list of certain diseases for which they recommend genetic testing, but for the vast majority of diseases, they conclude that there is “insufficient evidence to recommend for or against use.”
So what can the average person find out from one of these tests? Perhaps not as much as we thought. “For the vast majority of people who take personalized genetics tests, their results will have no predictive value,” said Klitzman.