Why ask the question?
The question implies a conflict, a potential incompatibility. If this doesn’t actually exist, then the subject is moot and we can all go home early. 

Proponents of complementary and alternative veterinary medicine (CAVM- also labeled “holistic,” “integrative,” “natural,” and many other terms we will explore shortly) typically claim that science and evidence support their practices. They recognize the marketing value of science, and they often assert that the conflict is a mere misunderstanding, or the result of ignorance, prejudice, or avarice rather than a true conflict between their approach and that of science-based medicine.

For example, the online College of Integrative Veterinary Therapies advertises its curriculum as “a wide range of evidence-based courses…bridging cutting edge science and tradition.”¹ A prominent proponent of so-called Traditional Chinese Medicine claims that integrative medicine “provide[s] comprehensive, evidence-based care that integrates the best of conventional and complementary approaches for the well-being of animal patients.”² You can read journals like Evidence-based Complementary and Alternative Medicine, or articles reporting clinical trials evaluating Reiki, “a biofield therapy currently used in hospitals worldwide [with] scientific evidence [that] supports its effectiveness in addressing many physical and emotional conditions.”³ Even the World Health Organization states that “Evidence-based complementary medicine has the potential to support mainstream medicine and more comprehensively support people’s health and well-being needs.”⁴

So what’s the problem? Why ask the question at all? Well, the problem is that despite both honest and disingenuous efforts to coopt the language of science and EBM, most of what we typically label CAVM is founded in beliefs and models of nature incompatible with a scientific understanding, and these practices are validated almost entirely by faith, personal experience, cultural tradition, and poor-quality efforts to mimic rigorous scientific investigation. EBM is more than a collection of jargon; it is an approach to knowledge that conflicts directly and forcefully with the philosophy underlying much of CAVM. 

Sometimes this divide can be bridged and truly scientific evaluation of CAVM methods can be undertaken. When this happens, the results mostly show these methods don’t work. In the rare cases where they do, they can, and should, simply become part of medicine, stripped of their mystical folk belief systems. In the words of two former editors of the New England Journal of Medicine, 

“There cannot be two kinds of medicine—conventional and alternative. There is only medicine that has been adequately tested and medicine that has not, medicine that works and medicine that may or may not work. Once a treatment has been tested rigorously, it no longer matters whether it was considered alternative at the outset. If it is found to be reasonably safe and effective, it will be accepted.”⁵

It is instructive to note, though, that proponents of CAVM often object to this type of deep acceptance, arguing it strips away the very core of what make their methods valuable. This illustrates the depth of philosophical incompatibility between science and most of CAVM. As these defenders put it: 

“Any CAM practiced its original way cannot be the same as its biomedical version.…If the biomedical paradigm is adopted, the system will have the characteristics of that paradigm- materialistic, mechanistic, reductionistic, linear-causal, and deterministic.”⁶

“Scientifically constructed ‘evidence’ for an alternative therapy only works when the therapy has mutated into a medicalized version and divested itself of its alternative philosophy. The very publication of trials can act as a reformulation of the very nature of a therapy, generally in the direction of medicalization.”⁷

The only reason CAVM exists as a category, then, is to highlight the special origins of certain practices as different from those accepted in science-based medicine. This serves both a marketing purpose (selling treatment that is “special” and “different” from conventional medicine) and also as an excuse for utilizing treatments without the type and level of evidence expected for mainstream medicine. 

Doctors who would never prescribe a new antibiotic with undisclosed ingredients and no clinical trial data showing safety or efficacy, one that is purported to kill bacteria by targeting its “energy signature,” will happily prescribe herbal or homeopathic remedies with no better evidence. The labels of “natural” or “traditional” are used as excuses to imply safety and effectiveness and evade the normal standards of evidence.

“By definition…complementary and alternative medicine…has either not been proved to work or been proved not to work. Do you know what they call alternative medicine that’s been proved to work? Medicine.
Tim Minchin”⁸

What is CAVM?
Before I go further, I should try to define CAVM. This is harder than it sounds because the term encompasses a variety of approaches that conflict with science-based medicine in different ways, to different degrees, and that often conflict just as much with each other. The unity, such as it is, lies not in any shared understanding of nature or of how medical therapies should be validated, though there is some broad agreement on elements of these. The real bond that connects CAVM approaches is their status as “other,” defined in opposition to science-based medicine. 

This opposition may be based on conflicting views of nature, competing cultural traditions, or simple part of a promotional strategy to distinguish oneself and one’s practices from other vets and what they offer. The “alternative” in CAVM was the original term for this loose collection of approaches, and it was meant to designate a replacement for conventional, science-based medicine. That proved too much for most human patients, and for most animal owners, who were mostly unwilling to abandon the obviously successful approach that brought us vaccination, antibiotics, and emergency rooms. 

This led to the adoption of the term “complementary,” suggesting it was beneficial to use unscientific or unproven practices alongside science-based medicine. This has been more successful, but proponents of CAVM dislike the implication that what they offer is an afterthought or second-rate compared with conventional medicine. This has led to the most successful label; “integrative medicine.”

The idea behind this label is that scientific and alternative therapies are different but equally useful tools available to veterinarians, and each should be used when appropriate without any distinctions based on their underlying theoretical rationales or history. The term suggests we can seamlessly blend alternative and conventional therapies, that they are equally useful and reliable tools we can select from for the medical job at hand. 

However, this obscures the reality that there are important practical and philosophical differences between how alternative and conventional therapies are developed, tested, and employed, and these differences matter. Integrative implausible, unproven, or demonstrably ineffective therapies with scientifically validated treatments adds no benefit for the patient, and it can even do harm. 

As infectious disease specialist Mark Crislip has put it, somewhat scatologically, “If you mix cow pie with apple pie, it does not make the cow pie taste better; it makes the apple pie worse.” (for those not familiar with the English idiom “cow pie,” it refers to bovine feces)

The Conflict: Philosophy
The core conflict here is philosophical. In terms of epistemology (the science of how we know things), proponents of CAVM largely reject the diagnosis of the disease EBM, and science generally, exists to treat. Forms of evidence viewed as weak and unreliable by EBM are privileged in CAVM, and those types of evidence higher on the pyramid are seen, at best, as nice to have but fundamentally unnecessary to support a given clinical practice. At worst, they reject the very idea that such evidence is more accurate or reliable than personal observation, anecdote, tradition, or pure faith. Science often serves only a marketing function in CAVM, not a meaningful role in choosing and rejecting ideas and practices.

Philosophically, CAVM relies predominantly on trust in personal belief and observation, and in the historical beliefs of individuals or previous generations of folk medicine practitioners. The most extreme proponents reject the hierarchy of evidence behind EBM entirely:

“[EBM] buttresses the idea that there is a legitimate hierarchy of knowledge and method with the [randomized control trial] as the gold standard and the clinician’s notes, observations, and judgments right down there in status with ethnography, sociology and anecdote…there are practitioners of naturopathic modalities who do not subscribe to this hierarchy at all”⁹

“For ancient and traditional healing modalities, one could argue that history provides the evidence on which to base clinical practice…One cannot conclude that, because a healing system cannot be measured conventionally, it is ineffective or unsafe.”¹⁰

“Users of homeopathy did not see a need for scientific testing and were happy with their own judgment of whether the treatment was working for them…[Randomized clinical trials] came at the bottom of their hierarchy of evidence.”⁷

“The invocation of a saint can cure intractable cancer; a voodoo curse can kill.… A shaman applying a curse does not consider it to be a placebo, nor does his victim. To them, real magic is involved…We can never prove the shaman wrong, only offer an alternative explanation.”⁶

“As a veterinarian now practicing homeopathy and chiropractic almost exclusively, I have all the proof I need every day in my practice to justify these modalities.”¹¹

Another key source of the incompatibility of CAVM and EBM is the problem of vitalism. At the heart of most alternative approaches, whether explicit or hidden, is a belief that living entities are defined by nonphysical energetic or spiritual forces, and health cannot be maintained or restored by any system that does not account for these forces. Homeopathy, chiropractic, Reiki and other “energy” therapies, traditional Chinese medicine (from which derive most of the forms of acupuncture practiced today), and many other CAVM approaches were born from this pre-scientific belief in spiritual forces as the cause of disease. 

While proponents of many of these methods have tried to paint over this idea with more modern scientific language (referencing quantum physics or bioelectricity, for example), the concepts often remain central to their practices. 

“Acupuncture reconnects and balances Life energy.… Energy medicines such as homeopathy, homotoxicology, Reiki, craniosacral therapy, and others align the physical, mental, and spiritual portions of the organism. Yes, I did say spiritual and that is a big part of holistic medicine—recognizing the spiritual nature of Life.”¹²

“pharmacological and surgical approaches appear incomplete…because they ignore the Vital Force which animates and breathes life into the biomachinery of living systems”¹³

“Because medical science has defined itself on a strictly physical basis, it is true that vitalism is unscientific. By definition, vitalism embraces a concept about a nonphysical force that can never be understood within the current scientific, medical paradigm.”¹⁴

“The belief that spiritual, emotional, psychological, or other non-measurable aspects of the individual patient’s presentation are important for healing does not require one to reject evidence obtained from clinical trials, but it does require the recognition that knowledge gained from such methods will be insufficient to guide optimal clinical practice…The importance of Qi in traditional Chinese medicine means that research that cannot and does not account for the force will never be compelling for a practitioner.”¹⁵

Even when disavowed, these mysterious forces leave gaps in causal reasoning left unfilled by scientifically legitimate concepts. Chiropractors have largely replace Palmer’s “innate intelligence” with the “vertebral subluxation complex,” but this has not been convincingly shown to exist.¹⁶ The “energy” behind Reiki and other supposed energy therapies cannot be detected except by those who already believe in it.¹⁷ And for all the thousands of pages devoted to finding a consistent, predictable reason why acupuncture should have beneficial clinical effects, no clear and compelling mechanism has been demonstrated.¹⁶ All of these methods, and even some more plausible CAVM practices such as herbal medicine and laser therapy, use scientific language to cover the core principle, which is some undetectable magical force inconsistent with a scientific understanding of physics and biology.

The Conflict: Practice
The most unfortunate aspect of CAVM is that it is largely defined and marketed in opposition to science-based medicine. Using it requires at least some level of acceptance of principles and forms of evidence not compatible with an evidence-based approach; and all too often it requires an outright rejection of mainstream medicine.

Use of alternative therapies is associated with less confidence in science-based medicine and less effective use of conventional tests and treatments.^18–20 This, in turn, is associated with poorer outcomes, such as shorter survival in cancer patients and greater risk of preventable infectious disease with vaccine refusal. While there is scant evidence to support claims that integrating alternative therapies with scientific medicine improves outcomes, it is clear that it can sometimes worsen them. 

Both the growing popularity of alternative treatments and the growing suspicion of science and science-based medicine stem from the same cultural and political factors, issues that have little to do with what is actually best for patients.

Ideally, every idea for assessment and treatment of our patients would go through the necessary steps of scientific evaluation: 

• development of a biologically plausible theoretical foundation compatible with established knowledge
• validation of this foundation and demonstration of possible benefits and risks in pre-clinical research
• testing in real-world patients through properly designed, conducted, reported, and replicated clinical trials

Not every step is always possible, and the evidence we have is often flawed and incomplete, for both science-based and alternative medicine. But this path is at least the aspiration of EBM, while is generally not seen as necessary or even desirable for CAVM. While EBM looks forward, developing new interventions and abandoning those that deserve to be left behind, CAVM looks backwards, mining the pre-scientific past for ideas and then setting out to create the impression of modern, scientific legitimacy without a genuine willingness to reject them if the data says we should.

Individual therapies may begin in the CAVM domain and pass into truly evidence-based practice. And some apparently science-based practices may drift into CAVM if evidence develops suggesting they should be abandoned but practitioners are unwilling to do so. However, for the most part CAVM and EBM will remain incompatible, oil and water, interacting but separated by incompatible philosophies, epistemologies, culture and politics, and fundamentally different views of how we should judge our practices.

References

1.         College of Integrative Veterinary Therapies. College of Integrative Veterinary Therapies. Accessed October 14, 2025. https://civtedu.org

2.         Marsden S. The New Era of Evidence-Based Medicine: Can We Survive It? American College of Veterinary Botanical Medicine Blog. May 11, 2025. Accessed October 14, 2025. https://acvbm.blog/2025/05/11/the-new-era-of-evidence-based-medicine-can-we-survive-it/

3.         Barbieri CR. Impact of Distant Reiki on Owner Assessment of Health and Wellbeing of Adult Dogs: A Blinded, Placebo-controlled, Randomized Trial. J Am Holist Vet Med Assoc. 78(Summer):11-19.

4.         Traditional, Complementary and Integrative Medicine. Accessed October 14, 2025. https://www.who.int/health-topics/traditional-complementary-and-integrative-medicine

5.         Angell M, Kassirer JP. Alternative medicine–the risks of untested and unregulated remedies. N Engl J Med. 1998;339(12):839-841. doi:10.1056/NEJM199809173391210

6.         Churchill W. Implications of evidence-based medicine for complementary and alternative medicine. J Chin Med. 1999;59:32-35.

7.         Barry CA. The role of evidence in alternative medicine: contrasting biomedical and anthropological approaches. Soc Sci Med 1982. 2006;62(11):2646-2657. doi:10.1016/j.socscimed.2005.11.025

8.         Minchin T. Storm. Orion Publishing; 2014.

9.         Jagtenberg T, Evans S, Grant A, Howden I, Lewis M, Singer J. Evidence-based medicine and naturopathy. J Altern Complement Med N Y N. 2006;12(3):323-328. doi:10.1089/acm.2006.12.323

10.       Curtis P. Evidence-Based Medicine & Complementary & Alternative Therapies. In: Curtis P, Gaylord S, Norton S, eds. The Convergence of Complementary, Alternative, and Conventional Health Care: Educational Resources for Health Professionals. UNC School of Medicine, Program on Integrative Medicine; 2004:Chapel Hill, NC. Accessed October 16, 2025. https://www.med.unc.edu/phyrehab/pim/wp-content/uploads/sites/615/2018/03/Evidence-Based-Med.pdf

11.       Jewell G. Comments on practising complementary and alternative modalities. Can Vet J. 2000;41(5):351.

12.       Kerns N. Alternative views on canine holistic dog care. Whole Dogs Journal. September 13, 2007. Accessed October 16, 2025. https://www.whole-dog-journal.com/care/alternative-views-on-holistic-dog-care/

13.       Stefanatos J. Introduction to bioenergetic medicine. In: Schoen A, Wynn S, eds. Complementary and Alternative Veterinary Medicine: Principles and Practice. Mosby; 1998:227-245.

14.       Knueven D. An introduction to holistic medicine. In: The Holistic Health Guide: Natural Care for the Whole Dog.TFH Publications; 2008:9-13.

15.       Tonelli MR, Callahan TC. Why alternative medicine cannot be evidence-based. Acad Med J Assoc Am Med Coll. 2001;76(12):1213-1220. doi:10.1097/00001888-200112000-00011

16.       McKenzie BA. Placebos for Pets?: The Truth About Alternative Medicine in Animals. Ockham Publishing; 2019.

17.       Rosa L, Rosa E, Sarner L, Barrett S. A Close Look at Therapeutic Touch. JAMA. 1998;279(13):1005-1010. doi:10.1001/jama.279.13.1005

18.       Johnson SB, Park HS, Gross CP, Yu JB. Complementary Medicine, Refusal of Conventional Cancer Therapy, and Survival Among Patients With Curable Cancers. JAMA Oncol. 2018;4(10). doi:10.1001/jamaoncol.2018.2487

19.       Cordonier L, Cafiero F. ?The link between interest in alternative medicine and vaccination coverage?. Rev Eur Sci Soc. 2023;611(1):175-197.

20.       Cramer H, Bilc M. Use of complementary medicine and uptake of COVID-19 vaccination among US adults. Front Med. 2025;12:1474914. doi:10.3389/fmed.2025.1474914

I am preparing a series of lectures for an upcoming conference, and it has given me a chance to reflect on some of the core ideas that have always driven this blog– the challenges created by our human limitations and the strategies we have develop to mitigate them.

This lecture attempts to illustrate what evidence-based medicine is and, perhaps more importantly, why we need it. In this current Age of Endarkenment, when science is under attack and misinformation is rampant, such reflection is more important than ever.

Our Shared Malady
Evidence-based medicine (EBM) is a treatment for a disease most of us don’t realize we have. It is both a preventative and a treatment, really, but it is not a cure. The best we can hope for is to manage the symptoms and minimize the damage done by our disease. 

The disease we suffer from lies in our brains. The mechanisms of observation and judgement we rely on as veterinarians to make recommendations for our patients are riddled with lesions. These have names like confirmation bias, cognitive dissonance, logical fallacy, and many others. The forms and manifestations of our disease are legion.^1,2

The consequences of our illness are, sadly, experienced mostly by our patients. Misdiagnosis, overdiagnosis, rejection of effective therapies and use of ineffective ones, and ultimately suffering and death that could, perhaps, be avoided if we sought treatment for our condition.

Like many medicines, EBM, can be bitter and uncomfortable to take. Many of us don’t know we need it, and even when we are diagnosed we may reject the treatment as too unpleasant. And there are potential adverse effects from treatment. A clear understanding of our limitations can be overwhelming, leading to despair and even therapeutic nihilism. However, the potential benefits are great and worth the risks.

Before I describe the treatment, I need to characterize the disease and convince you that you have it. This is especially difficult because the features of our malady include elements specifically inhibiting our ability to recognize it. Confirmation bias blinds us to evidence of our illness. Cognitive dissonance causes pain when we are forced to see and acknowledge such evidence. The Dunning-Kruger effect makes those of us least knowledgeable about the illness feel the most confidence that we are free of it. 

The best way to start on our journey may be with a story. Once there was a doctor, a kindly man who cared for children named Dr. Spock. He was an intelligent, caring doctor who brought great progress to the field of pediatrics and parenting. He wrote a book for parents called The Common Sense Book of Baby and Child Care,³ that sold millions of copies, was translated into 29 languages, and became a worldwide guide for parenting.

One key piece of advice Dr. Spock gave parents was that they should always put their babies to sleep on their stomach. Decades of experience, and simple common sense, showed Dr. Spock that doing so would reduce the risk of aspiration if an infant vomited, and this would help prevent Sudden Infant Death Syndrome (SIDS). SIDS is a terrifying and poorly understood condition in which apparently healthy babies die without warning, and parents are desperate for any action they can take to prevent it.

From the publication of Dr. Spock’s in 1946 until the early 1970s, the practice of putting infants to sleep on their stomachs was widely adopted, and parents were reassured by the confident recommendation of their doctors to follow this practice. 

However, by the 1970s, abundant research had accumulated showing this practice was a mistake. Babies sleeping on their backs were actually more likely to die of SIDS.⁴ Despite this evidence, the practice persisted until the early 1990s. For twenty years, parents around the world did the wrong thing, even after science had showed it was wrong, because of cultural inertia, confidence in respected authorities, anecdotal experience, and all the other sources of our confidence in mistaken beliefs.

A review published in 2005 found that heeding the evidence and abandoning the traditional practice sooner might have saved the lives of 10,000 children in the U.K. and 50,000 in Europe, the U.S., and Australasia.⁴ When educational efforts finally reached parents, and they began putting babies to sleep on their backs, the rate of SIDS dropped markedly.

Figure 1. SIDS rate versus prone sleeping rate in the United States, 1983 to 1995 (from Carroll, 1998⁵)

Does this mean Dr. Spock was a bad doctor? A fool? Were parents around the world stupid? No! This tragedy was a consequence of the illness we all suffer from- a natural tendency to see our personal observations and the stories told by others as compelling and reliable guides to reality, and a lack of a deep, effective appreciation of our limitations and the advantages of scientific data over anecdote and plausible reasoning. 

Evidence-based medicine is “the conscientious, explicit, and judicious integration” of controlled research evidence with our clinical expertise and judgement and the goals and values of our clients.^6,7 It is not a rejection of the value of the observations and judgements we make, but a recognition of their limitations and the dangers of trusting them too far. It is a set of methods and practices, yes, but first and foremost it is a philosophy, a perspective. “At its heart is the confidence in the scientific methodology that has developed over the centuries to enable us to distinguish what is likely to be true from what is likely to be false.”⁸ Diagnosing the illness, admitting we have a problem, is the necessary first step for starting treatment. I can teach you a bit about the treatment and how it works, but it won’t help you if you don’t begin by seeing that you need treatment.

Does EBM Work?
Proving that EBM is effective is not a simple matter. Where is the completely omniscient and objective observer who can judge that one approach to knowledge is better than another? Who would be willing to admit to practicing opinion-based medicine or belief-based medicine and then be willing to participate in a scientific study to show that their approach is better (or worse) than science? 

The best we can do is make some logical inferences, though I personally think these are quite compelling. Consider the change in human life expectancy over time (Fig. 2)

Figure 2. Life expectancy around the world

While this chart starts in the 18^th century, the available evidence suggests that the flat line, with  overall life expectancy less than 40 years, could be extended many thousands of years into the past. Figure 3 shows a major reason for this, which is the high proportion of human children who did not survive to adulthood for most of human history.

Figure 3. Childhood mortality.

For the vast majority of human history, most humans didn’t survive childhood (or childbirth), and we were plagued with parasites and infectious diseases, malnutrition, and a host of other acute and chronic ills. While a lucky few in each generation managed to live to old age, the great majority could expect only the Hobbesian reality of a “poor, nasty, brutish, and short” life. And then, in a mere handful of centuries, that changed.

Today, we enjoy a length of life and a state of health and wellbeing unimaginable to even the most fortunate of our ancestors. What changed? Did we evolve physically? Did the environment become more hospitable? The gods kinder?

The answer is simple and profound- science. All that changed was our ability to understand nature. Over centuries, we developed the methods of scientific thought and practice that led to a more accurate understanding of the causes of illness and death. And with that improved understanding came both new techniques for treatment and prevention, and also new methods for testing those techniques.

We are using the same brains our ancestors used. In our daily life, including in clinical practice, we still observe and reason as they did, and we make all the same errors. But we defer often enough to the picture of reality built by the community of scientists using scientific methods that we end with better information and making better choices.

EBM is just an extension of this set of methods. The basic steps, and all the detail and nuance embedded in them, are all simply a practical application of the principles and methods of science to clinical practice. Deciding, then, whether EBM is worth using depends largely on deciding whether science is better than the alternatives that preceded it. The alternatives most propose—relying more on clinical experience, tradition, or reasoning from theoretical principles- are the same that guided medicine in all the centuries before the changes in figures 2 and 3 began.

The Basics of EBM
The core of EBM in practice is quite simple. It consists of five basic steps-

1. Ask a question
2. Locate relevant evidence
3. Evaluate this evidence
4. Draw a conclusion
5. Assign a level of confidence

These steps are repeated as often as necessary until we feel we know enough to take action. They are repeated again whenever we have new questions, new evidence appears, or new action is needed. Entire textbooks have been written to guide us through these steps, but the basic process comes down to this.

The Question
The first step is to identify what we need to know to care for a given patient. What tests should we run? What treatment should we use? How can we tell if the treatment is working? What can we tell the owner about risks or prognosis? 

The key to getting useful answers from the scientific literature is asking useful questions. They should be specific enough to turn up relevant evidence but not so narrow that we exclude useful information. “Do antibiotics work?” is too broad to be meaningful. “Should we use amoxicillin, cephalexin, or enrofloxacin, for one week or for two weeks, in a 9 year-old neutered male Labrador retriever with an infected laceration from a stick on the front limb?” is not going to turn up many relevant clinical studies. Learning how to organize or ignorance and structure our questions is an EBM skill that can be developed, and there are many resources to support this.

Finding the Evidence
Another critical EBM skill is learning how to locate useful evidence. Sources as varied as textbooks, scientific journals, online databases and discussion forums, and even the vet working in the office next door are all available, and they all have their strengths and weaknesses. The best evidence is often the scarcest and hardest to access, while the most convenient sources often come with the greatest limitations. Locating and acquiring evidence requires us to be a bit like a detective or someone on a scavenger hunt, which can be fun but can also take time we don’t have. Building a collection of skills and resources over time can reduce the burden of finding useful evidence.

Evaluating the Evidence
It would be ideal if we could simply read a published scientific study or listen to the advice of our colleagues and immediately put the information we find into practice. Unfortunately, not all evidence is equally reliable, and even high-quality data may not apply to the patient in front of us. Critical appraisal of evidence is arguably the most important, and the least used step in this list. 

There are shortcuts that can help us. The classic pyramid of evidence in Figure 4 illustrates an approach to evidence that is sophisticated but academic and not always useful in practice.

Figure 4. Traditional evidence pyramid.

I prefer a simpler scheme which is more easily applied for most of us.

Figure 5. Practical evidence pyramid.

This emphasizes that all sources of evidence are potentially useful, but the closer we get to the top of the pyramid, the more confidence we can have in the information. Synthetic resources, such as clinical practice guidelines and systematic reviews, are especially valuable since they are both high in reliability and efficient, requiring less time, effort, and expertise to use effectively.

The Conclusion and the Confidence
Once we have gathered the available evidence and evaluated it, our main job is to decide what it means. What actions should we take or avoid based on the evidence? Just as important as the conclusion we reach is the level of confidence we assign to it. If I choose to say, “Here is a powerful therapy which will cure your cat,” that sets up very different expectations and behavior, in the owner and in myself, than if I say, “Here’s a therapy a few people have tried in dogs that might help your cat.” For reasons both practical and ethical, it is crucial that we choose and communicate an appropriate level of confidence for the recommendations we make.

Our disease drives us to have confidence greater than warranted by most of the evidence we are likely to have available. EBM gives us both a warning and some techniques for setting a more appropriate level, which then encourages more truly informed consent from our clients and probably more reasonable expectations and better followup.

The Madness and Wisdom of Crowds
Let us end with another story. On a cold Thursday morning in December, 1799, the former president of the United States, George Washington, rode out into the snow to inspect his farmlands.⁹ He was 68 years old, but strong and healthy for his age. That night he developed a bit of a sore throat, and by a day later he was having a hard time breathing. 

Unable to swallow a remedy of vinegar, molasses, and butter due to swelling in his throat, he accepted his doctor’s suggestion to remove a half pint (about 240mls) of blood from his arm. The patient did not improve, and the procedure was repeated several times over the day, with various doctors removing a total of about 3 to 4L of blood (about a third to half of the typical total blood volume for an adult man). Despite these heroic efforts, the former president died after about 13 hours of intensive treatment.

Bloodletting has been a routine and respected therapy in many cultures around the world and in many different historical eras. It is based on a simple powerful idea: What if we all illness stemmed from a derangement of a few essential factors, and we could prevent or cure illness simply by keeping these in balance? 

This idea is intuitively appealing, clear, and logical. It is also, of course, wrong. But every time it has emerged, it has captured the imagination and deep faith of the brightest medical and scientific minds, and persisted for centuries, even millennia, and into the present day.

A reasonable catchall name for this view is humorism. It was the rationale for the treatment of bloodletting promoted by Hippocrates in the 5^th century BCE and accepted by George Washington’s doctors in 1799. Some versions of humorism persist today in the theories of Traditional Chinese Medicine and Indian Ayurveda.

There have always been skeptics of bloodletting. George Washington’s wife opposed the practice and begged his doctors not to take so much blood from her husband. But the logic of humorism and the innumerable anecdotes of patients cured by the practice overcame such skepticism. As late as 1875, defenders of the practice argued for it with reference to such compelling evidence:

“Who is there with ten or twenty years experience in the profession, that has not seen the most marked advantages from bleeding…” asked one such defender.¹⁰ Another learned physician wrote that, “He thought it really saying too much…that we should assume to be so much wiser than our fathers, who had lent their approval to a custom that had been sanctioned by ages of experience.”¹⁰

Eventually, the current models of physiology and disease replaced humorism, and the methods of science replaced bloodletting with a range of practices that, while imperfect, have nearly doubled human life expectancy and brought levels of health and comfort unimaginable in most of human history.

So were all our “fathers” bad doctors? Fools? No! This story is meant to show the unique and challenging nature of our disease. It is both congenital, built into each of our brains from birth, and also communicable. The manifestations of this illness in each of us magnifies the symptoms in others, and in a population the disease can make us sicker and do more harm that in one isolated patient. We can reinforce and sustain each other’s beliefs, even if they are egregiously wrong.

Fortunately, the same power of the community lies in the treatment for our illness. Science is a community process in which we pit our limited, imperfect, biased notions against each other in a competition judged by the strength and consistency of the data we can produce. Though the madness of crowds¹¹ can lead us horribly astray, the wisdom of crowds¹² can rescue us from our individual delusions. The secret is to harness the competition of ideas in a race governed by the rules and standards of science and evidence. 

Evidence-based medicine is a part of the larger project of using science to control our illness, to keep us closer to the truth of nature so we can help our patients most effectively. 

Key Points

• Human observation and judgement is inherently flawed, and our confidence in our reasoning is typically greater than the true accuracy of our beliefs.
• Evidence-based medicine (EBM) is a facet of the greater project of science. It is a set of perspectives and practices meant to improve the accuracy of our understanding of nature and set appropriate degrees of confidence around our beliefs.
• The five basic steps of the EBM method are-
  • Ask a question
  • Locate relevant evidence
  • Evaluate this evidence
  • Draw a conclusion
  • Assign a level of confidence

This is an iterative process, repeated often as our information needs and the available evidence change.

• Groups of humans can strengthen and persist in false beliefs for generations. 
• Groups of humans can also develop more accurate understanding of nature if guided by the methods of science
• Individual clinicians can benefit from EBM by
  • Maintaining an awareness of our disease and its consequences
  • Following the steps of EBM
  • Relying on the work of a scientific community more than on individual personal experience and belief

References
1.         Kida T. Don’t Believe Everything You Think. Prometheus; 2006. Accessed October 9, 2025. https://www.simonandschuster.com/books/Dont-Believe-Everything-You-Think/Thomas-E-Kida/9781591024088

2.         McKenzie BA. Veterinary clinical decision-making: cognitive biases, external constraints, and strategies for improvement. J Am Vet Med Assoc. 2014;244(3):271-276. doi:10.2460/javma.244.3.271

3.         Spock B. The Common Sense Bookf of Baby and Child Care. 1st ed. Duell, Sloan, ad Pearce; 1946.

4.         Gilbert R, Salanti G, Harden M, See S. Infant sleeping position and the sudden infant death syndrome: systematic review of observational studies and historical review of recommendations from 1940 to 2002. Int J Epidemiol. 2005;34(4):874-887. doi:10.1093/ije/dyi088

5.         Carroll JL, Siska ES. SIDS: counseling parents to reduce the risk. Am Fam Physician. 1998;57(7):1566-1572.

6.         Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS. Evidence based medicine: what it is and what it isn’t. BMJ. 1996;312(7023):71-72. doi:10.1136/bmj.312.7023.71

7.         Straus SE, Glasziou P, Richardson WS, Haynes RB. Evidence-Based Medicine: How to Practice and Teach EBM. 5th ed. Elsevier; 2019.

8.         Cockroft PD, Holmes MA. Handbook of Evidence-Based Veterinary Medicine. Blackwell; 2003.

9.         Vadakan V. The Asphyxiating and Exsanguinating Death of President George Washington. In: 2004. Accessed October 9, 2025. https://www.semanticscholar.org/paper/The-Asphyxiating-and-Exsanguinating-Death-of-George-Vadakan/33f243e97580948b73e700df9489906a37849247

10.       McKenzie BA. Placebos for Pets?: The Truth About Alternative Medicine in Animals. Ockham Publishing; 2019.

11.       Mackay C. Extraordinary Popular Delusions and the Madness of Crowds. chard Bentley; 1841.

12.       Surowiecki J. The Wisdom of Crowds. First Anchor books edition. Anchor Books, a division of Random House, Inc; 2005. Accessed October 9, 2025. http://catdir.loc.gov/catdir/samples/random051/2003070095.html