One of the stranger call-ins on my interview with Kathleen Dunn last month was when a woman who proudly declared that she was a math major in college asserted that 23andMe had told her she wasn’t at risk for many diseases which now in her 60s she had developed. I didn’t want to be too pointed about it, but if you are in your 60s you are at risk for developing many illnesses no matter what your “genetic risk.” This is clear from 23andMe’s statistics, which display high baseline risks for many common diseases. From reading comments on 23andMe discussion forums it seems that perceived false negatives are going to be a much bigger issue than false positives over the long run. If the tests are “wrong” in a direction which leaves you in a better state than predicted you might feel like you’ve dodged a bullet. On other hand if the tests are “wrong” in a direction which gave you false comfort, or add insult to injury when you’ve developed a debilitating disease, then you feel much more burned.