 While false positive results, pain during the procedure and radiation exposure, may be among the most frequent harms associated with mammogram screening, the most serious downside is now recognized to be something called overdiagnosis. So serious, as the raise of the question, does it make the whole thing worthless? The value of doing routine mammograms at all is being questioned due to overdiagnosis, which is the diagnosis and treatment of breast cancer that would never have become a threat to a woman's health or even apparent during her lifetime. See, people think that once you have a cancer cell in your body, it will progress predictably and inevitably to a terrible death, and that's simply not true of most cancers. Some cancers may outgrow their blood supply, become starved and wither away, others may be recognized by our immune system and successfully contained, and some are simply not that aggressive in the first place, meaning yeah, it may continue to grow unchecked, but so slowly that it would be like 200 years before it was big enough to cause any problems, and so in effect you die with your tumor instead of from your tumor. Indeed, if you do autopsy studies of young and middle-aged women who just happened to die in a car accident or something, 20% of them had cancer in their breast, so like 1 in 5 women are walking around with breast cancer. Now that sounds a lot scarier than it is. Since at that age range, the risk of dying from breast cancer is less than 1%. In fact, your risk of ever dying from breast cancer in your lifetime is less than 4%, which goes to show that many of these cancers they found incidentally, in fact most of them would likely just fizzled out on their own. The problem is we continue to have a 19th century definition of cancer, dating back to the 1860s. See, cancer is defined by what it looks like under a microscope, not by what its subsequent behavior is. So yeah, using that definition, 1 in 5 of these women technically had cancer, like this 30-year-old here, but that doesn't necessarily mean it would go on and do anything. The question then becomes, if it's so common, do you even want to know about it? If it's going to progress and cause a problem, then definitely, catching it early could save your life. But if it's never going to grow, if it's going to remain microscopic, then finding it could actually be bad for you. They'd be like, look, you have cancer, we have to treat it, surgery, chemo, radiation, whatever it takes. Then you'd suffer all the physical effects of treatment, the psychological hell of fearing for your life, all completely unnecessarily, if in fact it was never going to cause a problem. That's over diagnosis. These kinds of car accident-type autopsy studies show that between 7 and 39% of women, ages 40 through 70, are walking around with tiny breast cancers. 30 to 70% of men older than 60 have prostate cancers, and up to 100% of older adults have microscopic cancers in their thyroid glands. Yet only 0.1%, 1 in a thousand ends up suffering or dying from thyroid cancer. Normally it just sits there, doesn't do anything. Likewise, even though the majority of older men may have tiny cancers in their prostates or a significant number of women in their breasts, the lifetime risk of death or cancer spread is only about 4%. So if you had a magic wand that could pick up cancer with 100% accuracy and waved it in front of people, your over diagnosis rate, the probability that the prostate cancer you'd pick up would have turned out to be harmless, is like 90%. And nearly every single thyroid cancer and a significant proportion of breast cancer cases, that's why screening for these cancers can be tricky or even potentially dangerous, since in many cases, sometimes most cases you have been better off if they had never found it. Now this is not true for all cancers. There's little evidence of over diagnosis for cervical or colorectal cancer, for example. Those cancers do seem to just keep growing, so the earlier you catch them, the better. Institute pap smears and cervical cancer death rates plummet, and just a single sigmoidoscopy between the ages of 55 and 65 may decrease one's risk of dying from colorectal cancer by up to 40%. Whereas some studies show that even getting mammograms every year don't appear to reduce breast cancer mortality at all. But if we assume a 15% drop and a 30% over diagnosis rate, which is what most studies have found, then that would mean for every 2,000 women invited for mammograms for 10 years, one will have her life prolonged, and 10 healthy women would be overdiagnosed. In other words, they would not have had a breast cancer diagnosed if they had skipped screening, but were instead treated for breast cancer unnecessarily. And about 1,000 would have gotten false alarms, which can be stressful while you wait for the results, but the harms caused by becoming a cancer patient unnecessarily can be lifelong, and even mean a shorter life. It's important to be aware that some of the needlessly treated women will die from that treatment. For example, radiation treatments can't help but penetrate down into the heart as well, increasing the risk of the number one killer of women, heart disease. This raises questions about doing routine mammograms period as it converts thousands of healthy women into cancer patients unnecessarily some of whom may not make it out alive. Ironically, though, those who do become mammographies biggest cheerleaders thinking mammograms saved their life. The mammogram found a cancer they didn't even know you had, and yeah, the treatment was rough surgery, radiation, drugs, but it worked. Life was saved. Thank God she got that mammogram. You should too. Whereas actually, the more likely scenario, in fact maybe the 10 times more likely scenario, is that the treatment didn't do anything since the cancer wouldn't have hurt you anyway. So you went through all that pain and suffering for nothing. That's the crazy thing about mammograms. The people who are harmed the most are the ones who claim the greatest benefit.