Physicians face a host of challenges in practice, but the one that looms largest is often this — they don’t know everything.

It would be tempting to think that they do. As patients, we want them to. We want our doctors to tell us that they know what’s wrong and how to fix it. Medical mysteries are fun on television, but in our real lives, they’re profoundly unsettling and can have long-ranging consequences.

Given that doctors don’t know everything — that they can’t because the breadth and depth of scientific knowledge has its limits, despite how quickly those limits shift — what do doctors then base their practice on?

We would hope it would be the most cutting-edge research. Or would we? The problem with cutting-edge research is that, in order to be certain that a finding is correct, it takes time. It takes replication of that finding. We’re certain, or as certain as we can be, that lowering blood pressure is good for people at risk of heart attack. We have an enormous body of scientific literature on this question. But we still run into questions about the details that we don’t have good answers to: How much should we lower blood pressure? What factors about a person dictate what blood pressure goals they should aim for? There was a recent kerfuffle over lowering the cutoff for “high blood pressure,” and doctors are still vigorously debating whether there’s any use in changing that definition.

So if we use cutting-edge research, we may make mistakes. We may be wrong about what interventions help, how much they help and who might find them helpful. If we stick with the research that’s been replicated time after time, we miss out on some of the insights of the new research. It’s also worth noting that keeping up with new research is more than a full-time job; no individual doctor can reasonably read and apply all the research that comes out. This is why there are groups that specifically tackle subject reviews so doctors can look at a single source for the best available information on a topic, but those reviews can’t be constantly updated, either — there is simply too much research happening to keep up.

That is a good thing! We want more research. We want to keep pushing forward on finding out what advances medicine can make. But it means that individual doctors are always behind, always at a disadvantage.

How do doctors deal with this? Doctors incorporate knowledge from many sources to create their own expertise. There’s the book-learning from the first two years of medical school, the clinical learning from later medical school and residency, their own experiences with patients, the updates in whatever scientific journals they follow, news stories that open up topics, conversations with other doctors who have learned about something new, conferences, formalized continuing medical education credits that are required to maintain licensure, patients themselves who live with conditions the doctor hasn’t seen before — the list goes on.

Doctors create, update and curate their expertise. They develop definite ideas about why certain things happen and the best way to treat those problems. Not all of this is grounded in the kind of hard scientific data we would like to have for every problem. Sometimes it’s because that data doesn’t exist. Sometimes it’s because that specific doctor doesn’t know the data. Sometimes it’s because the doctor continues to believe something in spite of the data. And that last one can take patients by surprise.

Why would a doctor — with over a decade of medical education under their belt — continue to believe something that’s directly contradicted by the data?

One likely answer is cognitive dissonance. If a doctor — whose mission in life is to help patients — discovers that something they have been doing is not helpful or has a greater potential to harm, they can respond in one of two ways. They can either incorporate this new information into their worldview and change their clinical practice, or they can reject it. The dissonance between wanting to help and not helping has to be resolved in some way.

Incorporating new findings into practice can be challenging. Doctors have to be comfortable with ambiguity and with acknowledging the limits of their expertise. They may have to learn new skills. They may face patients they have known for years who are now confused by the change in their care, who are concerned that their doctor wasn’t doing the right thing before with the ugly specter of malpractice in the air. Having those conversations is difficult, and doctors get very little formal training in communication. They may face the possibility that they have directly caused harm to patients. With the best of intentions, certainly, but real harm nonetheless.

Alternately, they can reject the new information. They can point to the very real flaws in the scientific process as it currently exists and say that the data is inadequate. They can point to their clinical experience, which is subject to all the recall biases of the human mind. They can reiterate the theoretical reasons why the intervention was supposed to work in the first place. And they can keep doing something that’s been shown to have no real benefit to patients.

This is a problem in every field of medicine. Some are worse than others; obstetrics is notoriously difficult to change because the stakes are so high and the research is so limited. But all physicians face the possibility that something they do today as a matter, of course, will, in five or ten or fifteen years, be revealed to cause more harm than good.

Doctors need to be aware of the natural human tendency to suppress their discomfort around having possibly harmed patients, particularly when that means ignoring or denying new research that is actually compelling on its own merits. Resolving cognitive dissonance with denial makes us feel better but at the cost of not honoring the physician’s role.

Kristin Puhl is a medical student and can be reached on Twitter @kristinpuhl.

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