These examples are a reminder of the need for ongoing research, humility, and the willingness to challenge established beliefs for the sake of patient care.

Medical certification and licensing boards also claim that individual healthcare providers who share information that is contrary to “consensus-driven scientific evidence” are misinformation spreaders who cause so much potential harm that their certifications or licenses should be revoked. While some might argue in favor of the merits of consensus in providing timely guidance, it is important to correct for the many potential biases, beliefs, preferences, and conflicts of interest that could lead to subjective consensus decisions, and to ensure that consensus-based recommendations reflect the views of a heterogenous and diverse group of experts. How can it be a consensus when all sides of an issue have not been considered and differing views are being censored? What about all the out-of-the-box thinkers in history who have challenged conventional thinking and moved the needle forward for all humankind? Consensus is, in fact, a perfect cover for conflicts of interest like ties to pharmaceutical companies, medical device manufacturers, or other commercial entities, which compromise the integrity and impartiality of the consensus process. Or, some experts may be more inclined to favor consensus recommendations aligned with the interests of their research funding sources. Others may have intellectual biases based on long-standing beliefs or theories they are hesitant to challenge. And what about all the times in medical history when consensus beliefs were proven wrong, and patients were harmed in the process because the establishment clung to a flawed premise? Once a consensus is reached, there is often resistance to updating recommendations based on new and emerging evidence, which leads to guidelines becoming quickly outdated and not reflecting the latest advances in science. Studies have shown that even after claims have been disproven in the medical literature, they often persist for years and even decades before they retreat from use. Dr. David Sackett, considered one of the ‘fathers’ of evidence-based medicine, once had this advice for medical students:

Half of what you’ll learn in medical school will be shown to be either dead wrong or out of date within five years of your graduation; the trouble is that nobody can tell you which half – so the most important thing to learn is how to learn on your own.”

[Incidentally, Sackett also cautioned students to “remember that your teachers are as full of bullshit as your parents,” but that’s a topic for another article!] Here are 25 times the medical consensus had to be revisited. This list is in no particular order and is by no means exhaustive. We share these examples simply as a reminder of the need for ongoing research, humility, and the willingness to challenge established beliefs in the pursuit of patient-centered healthcare. 1. Thalidomide and Birth Defects (1950s-1960s) In the late 1950s and early 1960s, thalidomide, a sedative, and anti-nausea medication, was widely prescribed to pregnant women to alleviate morning sickness. Regrettably, it was believed to be safe for use during pregnancy, even though some animal studies indicated potential risks. Tragically, thousands of babies were born with severe limb deformities, known as phocomelia, because their mothers took thalidomide during pregnancy. This devastating outcome exposed the flaws in the medical consensus of the time and led to the establishment of stricter drug safety regulations.

2. Hormone Replacement Therapy (HRT) and Cardiovascular Disease (1990s-2000s)

HRT was commonly prescribed to postmenopausal women during the 1990s and early 2000s to alleviate menopausal symptoms and prevent cardiovascular disease. However, a large-scale study called the Women’s Health Initiative (WHI) conducted in 2002 found that long-term use of HRT was associated with an increased risk of heart disease, stroke, blood clots, and breast cancer. This overturned the prevailing belief that HRT was a protective measure against heart disease and underscored the need for rigorous testing of treatments before widespread adoption. The medical consensus on HRT for menopausal symptoms underwent a significant revision in the early 2000s, shifting towards limited and individualized use of HRT for symptom management and only for the shortest duration necessary. 3. Stomach Ulcers and Stress (20th Century) For much of the 20th century, the medical consensus held that stomach ulcers were primarily caused by stress, spicy foods, and excessive acid secretion. However, in the 1980s, Australian scientists Barry J. Marshall and Robin Warren discovered that the bacterium Helicobacter pylori was responsible for most stomach ulcers. Despite facing skepticism from the medical community initially, their findings eventually led to a paradigm shift in ulcer treatment, with antibiotics becoming a crucial component of therapy. 4. Dietary Fat and Heart Disease (1970s-1990s) For several decades, there was a widespread belief among health professionals that dietary fat, particularly saturated fat, was the primary cause of heart disease. Consequently, low-fat diets gained popularity as a means to reduce cardiovascular risk. However, later research, such as the large-scale PURE study published in 2017, questioned this consensus, suggesting that excessive carbohydrate consumption might play a more significant role in heart disease risk than previously thought. This revelation challenged long-standing dietary guidelines and led to a reevaluation of the relationship between fats, carbohydrates, and heart health. 5. Smoking and Health Risks (20th Century)

For much of the 20th century, the tobacco industry worked tirelessly to cast doubt on the harmful effects of smoking, while medical professionals were slow to recognize the dangers. Smoking was initially endorsed and even advertised as a harmless or health-enhancing habit. It wasn’t until landmark studies, such as the 1964 Surgeon General’s Report, that smoking was unequivocally linked to lung cancer, heart disease, and a myriad of other health issues. The battle against tobacco use highlighted the dangers of delaying action due to industry influence and the importance of evidence-based decision-making in public health. 6. Cholesterol and Heart Disease Risk (20th Century – 21st Century) For many years, the medical consensus held that high cholesterol levels, specifically LDL cholesterol, were a primary risk factor for heart disease. However, more recent research has revealed that it is not just the total cholesterol levels that matter, but also the ratio of LDL to HDL cholesterol, as well as other factors like inflammation and triglyceride levels. This led to a shift in focus from solely targeting cholesterol levels to a more comprehensive approach to assess cardiovascular risk. 7. Bloodletting (Ancient Times – 19th Century) Bloodletting, the practice of deliberately withdrawing blood from a patient, was a widely accepted medical treatment for various illnesses in ancient times and throughout the Middle Ages. It was believed to restore the balance of bodily humors. However, with advancements in medical knowledge, the practice was eventually recognized as ineffective and potentially harmful, leading to its abandonment. 8. Prostate-Specific Antigen (PSA) Testing for Prostate Cancer (1990s – Present) PSA testing was initially hailed as a revolutionary tool for the early detection of prostate cancer. However, over time, it became evident that PSA testing led to overdiagnosis and overtreatment of low-risk prostate cancers. As a result, the medical consensus has evolved to be more selective in recommending PSA testing, taking into account individual patient risk factors. 9. Opioid Prescribing for Chronic Pain (Late 20th Century – 21st Century)

There was a time when opioids were commonly prescribed for various types of chronic pain conditions. However, the opioid epidemic that followed highlighted the dangers of overprescribing and the potential for addiction and overdose. The medical consensus has since shifted towards more judicious and cautious use of opioids for chronic pain management, emphasizing alternative treatments and multidisciplinary approaches. 10. Dietary Recommendations for Saturated Fat and Sugar (20th Century – 21st Century) As our understanding of nutrition has evolved, so have dietary recommendations. The once-held belief that saturated fat was the primary cause of heart disease has been challenged, and more emphasis is now placed on the type of fat and overall diet quality. Similarly, growing evidence on the negative health effects of excessive sugar consumption has led to updated guidelines and warnings about sugar intake. 11. High-Dose Chemotherapy and Bone Marrow Transplant for Breast Cancer (1990s) In the 1990s, high-dose chemotherapy followed by autologous bone marrow transplant was considered a promising treatment for advanced breast cancer. However, subsequent research did not demonstrate a significant improvement in survival rates compared to standard chemotherapy. The medical consensus shifted away from high-dose chemotherapy as a routine treatment for breast cancer due to its increased toxicity and lack of survival benefit.

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12. Bed Rest for Low Back Pain (2010s) For many years, the medical consensus advised bed rest as a common treatment for low back pain. However, research in the 2010s revealed that prolonged bed rest could lead to muscle deconditioning and delay recovery. The revised consensus now recommends staying active and engaging in gentle exercises for most cases of acute low back pain. 13. Screening Mammography Guidelines (2000s-2010s) The recommended age and frequency for mammography screening have been subject to revision over the years. Earlier consensus guidelines suggested annual mammograms starting at age 4