I used to think medicine would get easier over time. It makes sense, right? You see patterns, you learn how treatments work, and you just get to know stuff. Experience should make it easier to diagnose and treat.

That’s not been the case for me. In fact, it’s closer to the opposite. In the exam room, as I look up to the patient from my stool, and before I stand at the white board to explain, I often find myself pausing for a moment to think: Is this really the right course? Does the evidence support doing it this way? Do I know the science, or is it “just the way things are done?” I have the same problem in the hospital—perhaps worse, as there, dogma permeates most of what we do.

What keeps popping into my head is the hubris of medicine. As I grow older, the excessive pride and confidence of the medical establishment becomes more obvious. Why didn’t I see it before?

In many cases, medical and surgical treatments that were once thought to be beneficial turn out to be not so. Often, these therapies were backed by expert guidelines and taught to young students as law. Think of that for a moment. We do things to people; we monitor, we medicate, and we even cut, all with the aim of helping. But then further study proves that we were actually providing no benefit and in some cases, causing harm.

This is sobering.

A recent article, published in Mayo Clinic Proceedings, provides chilling evidence that many well-established medical practices are wrong. Researchers from the National Institutes of Health looked at 10 years of clinical investigations from the New England Journal of Medicine. Over the past decade (2000-2010), they found 363 published studies that evaluated an established therapy.

In 146 of the 363 studies (40%), the scientific evidence caused a reversal of established medical practice. That’s a sterile way of saying that nearly half the time the prevailing wisdom was wrong. It is worth going over some examples. Not one branch of medicine was spared a reversal.

In my field, electrophysiology, the AFFIRM trial revealed that the strategy of using rhythm control drugs to maintain sinus rhythm in elderly asymptomatic patients with AF did not reduce stroke, hospitalization and death rates. To this day, nearly ten years out, I still see AF patients on rhythm drugs because a doctor thinks this strategy will prevent stroke or reduce the risk of death.

In interventional cardiology, the idea that coronary blockages need to be ‘fixed’ is ingrained. Fueled by favorable reimbursement, intense marketing from industry and an insatiable public demand for being ‘fixed,’ stent implantation has soared. Then the COURAGE trial showed that implanting stents in patients with asymptomatic coronary disease was no better than optimal medical therapy and lifestyle modifications. Again, to this day, wide variations in cardiovascular care suggest too many doctors ignore scientific evidence.

Preventative cardiologists also took their share of lumps. Hormone replacement therapy for women was perhaps the most famous reversal. Millions of women were treated with hormones under the guise that manipulating female hormones would be “cardio-protective.” But HRT was based only on observational studies. Randomized clinical trials proved the concept wrong.

In pediatrics, therapy of inner ear infections set the stage for a huge medical reversal. Doctors were fearful that recurrent otitis media would cause long-term hearing loss. Guidelines recommended early intervention with surgery (tubes) to prevent complications. But then two major trials showed no benefit. One of the most commonly done procedures in all of pediatrics — wrong!

In ICU medicine, the pulmonary artery catheter (Swan-Ganz) was thought to provide invaluable data on a patient’s heart and lung function. You just couldn’t manage a sick patient without one. Surgeons, too, thought the balloon-tipped catheter was necessary for major operations. Then, when it was studied systematically, no benefit was found. A generation of doctors toiled over those pressure tracings — all for naught.

Cardiac surgeons do not like bleeding after they close a chest. An almost magical (procoagulant) drug called aprotinin was found to decrease post-op bleeding. Not until after the use of aprotinin became established practice did four studies refute its benefit. Here the story gets worse. Aprotinin increased mortality.

In anesthesia, one of the more feared complications is patient awareness of surgery. It’s a terrible outcome, which, in some cases leads to PTSD. It was no surprise then that anesthesiologists jumped at the chance to use a nifty little monitor stuck on a patient’s scalp. The bi-spectral index monitor quantifies the deepness of a patient’s sedation during surgery. Despite only one industry-sponsored study, use of the monitor surged, and it nearly became a standard of care. Then in 2008, a large randomized trial showed no benefit.

Medical reversals in oncology were especially sad. Thousands of women with advanced breast cancer were exposed to unnecessarily aggressive surgery or chemotherapy (with stem-cell transplantation) before careful clinical trials showed no benefit. Metastatic breast cancer is bad enough; heaping this therapy on at the end of life was tragic.

In diabetes care, we learned the hard way that strict control of blood glucose in hospitalized patients worsened outcomes. I remember the medical staff meetings where protocols designed to micro-manage blood sugars were presented. The experts were sure. Blood sugar had to be strictly controlled. Wrong again. Too much action caused harm.

I could go on. There are many more examples. A total of 146 similar narratives are available. Reversals included medicines, procedures, diagnostic tests, screening and medical devices. If an intervention was not based on solid scientific evidence, there was a nearly 50% chance it was wrong. What’s more, some of the most striking reversals came when therapy was aggressive.

The authors emphasize three reasons why medical reversals are so serious.

First, millions of humans were harmed.

The second issue is continuing harm. Some estimates suggest it takes ten years — on average — to change entrenched medical practice. Believe me, ten years may be an underestimate.

Third, medical reversals cause harm because they erode trust in the patient-doctor relationship. Patients expect doctors to be either correct, or transparent about uncertainty. You have seen how the erosion of trust can lead to patients refusing beneficial therapy. (Think vaccines.)

Four important messages stand out:

1. Doctors must strive to be better judges of science. When we intervene, especially in an aggressive way, with procedures, or surgery, or potent chemicals, we must be sure the science backs us up. Our interventions should never be eminence-based, but rather, evidenced based.

2. Hubris has to go. Though there is a role for ‘assess and decide’ in the practice of medicine, we must become more honest and skeptical with ourselves. Let’s get comfortable with uncertainty. This way, we can better communicate with our patients. When a prescribed therapy merely makes sense (or is just a good idea), all involved parties should proceed with caution.

3. This data should reset the default of American medicine. Currently, most everyone expects action, intervention and monitoring. Do something doctor! This needs to change — immediately. Our default should be to intervene and monitor only when the evidence supports doing so. These findings call us to share decisions with patients and default to a culture where less is more.

4. This is not just important information for doctors. Patients seeking medical treatment should not assume a prescribed therapy is beneficial just because a doctor says it is. The era of paternalism in medicine is over. Patients should be able to ask their doctor whether the evidence supports the intervention. It’s okay if the doctor is uncertain. In fact, doctors who are too sure of things worry me.

Make no mistake, the fury of modern medicine is a beautiful thing. It’s a great time to be a patient and a doctor. Whenever it comes time to act, however, it seems healthy to consider what the next generation of caregivers will think of our plan. I’m sure prescribing good food, good exercise, good sleep and good attitudes will stand the test of time. I’m not so sure about a lot else. If ear tubes and tight control of diabetes don’t stand up, what will?

John Mandrola is a cardiologist who blogs at Dr John M.