Are DNA testing services like 23andMe something good to do and show your doctor for preventive reasons? What are the downsides?

What 23andMe and other similar services offer is a comparison between your own genes and those of the general population. You can think of genes as a code or a blueprint inside each cell in your body- they tell the cell how to build and conduct itself. For the most part, we all have the same genes, but our differences come from small variations within them. These variations help determine things like natural hair color and height. Being able to tell the difference between your genes and other’s is not the hard part, though (they can do this with great accuracy), it is telling what these difference mean that is more difficult. Here are the reasons why: 1) Every characteristic that we have is not only determined by genes, but also by how you were raised and what your body is exposed to on a daily basis. 2) In order to give you useful information about a particular set of differences in your genes, somebody needs to have researched how that translates into your unique qualities- does it make you less likely to have freckles?, more likely to have breast cancer?, etc. You may have one gene difference that increases your risk for skin cancer and one that decreases it, but deciding what the two mean together is not usually as simple as addition and subtraction, and the studies that have been done don’t often look at those specific interactions. Suffice it to say- it’s complicated 3) The science of genetics rapidly changes from year to year. So- this year, your risk for developing Alzheimer dementia in the future may be 5%. Next year, based on new studies, it might be 10%, the year after, it might be 3%. If you maintain a subscription to these services, you could get updates, but these updates might be sending you on a rollercoaster ride. 4) Sometimes what you don’t see can be falsely. If you are worried that you might get breast cancer, the testing service might tell you that you don’t have any of the genes that increase your risk. That sounds great, but the reality is that the test only tests for certain genes that increase risk for breast cancer, even though many others are already known. So- even if the science advances, costs and other factors may limit the testing service from using all available data. Because of these problems, DNA testing can’t answer questions like, "Is my real father is John Doe?", "Will I get dementia?", or "Will I get breast cancer before I am 60?". Rather, it tells you less straightforward, less helpful things, like, "My risk of diabetes is as low as 8% and as high as 52%... if I am a male of European decent", and "There is a 44% chance that Genghis Khan is my ancestor". In addition, there are other factors that make the tests difficult to interpret and difficult to use in making decisions about your health. As the science improves, testing will likely get better over time and so will the decisions that we can make based on it. My opinion is that this testing is not yet ready for the consumer. Not all doctors agree with me, so I would recommend discussing it with a doctor who knows you well before deciding whether to go through with it.