When some people form an opinion, it can be nearly impossible to get them to change it. You know the kind: It doesn’t matter what facts, figures, statistics, evidence, or reality you present to these people — the info is no match for their set-in-stone mentality.

This mindset was studied recently in “The Power of Priors: How Confirmation Bias Impacts Market Prices,” a book by Tom Gruca, a marketing professor at the University of Iowa, and Michael Cipriano, an associate professor of accounting at the University of South Carolina Upstate. Over a 10-year period, student traders purchased and sold real-money contracts in the Iowa Electronic Markets, predicting how successful new movies would be during the first four weekends. Even if the first weekend’s box office receipts showed the movies were not as successful as predicted, the student traders were unlikely to make adjustments based on the new information.

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There are very real consequences of this “confirmation bias” (or just plain stubbornness) when it comes to our health.

Confirmation bias happens when people look for information to confirm their original view — and reject or ignore new information that challenges their original theory.

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Nikki Martinez, a Chicago-based psychologist and licensed clinical professional counselor, said she often sees clients dealing with this issue.

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“People will cling to what they have been taught, what they have been raised to believe, and what brings them physical joy,” she said.

“The percentage of people who will actually take the extra steps to research a matter or health concern, and make changes to the patterns they have been implementing in their lives for years, is quite small. They choose to either not believe it, or simply ignore it, as it does not fit the comfort of what they have come to know. To take a medication, eat healthfully, exercise, or stop smoking does not naturally fit for people who have been doing things a certain way for years,” added Martinez.

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Unless there is personal experience with a particular medical issue, in fact, it may be nearly impossible to get some people to alter their views or behaviors.

“I have seen many individuals who have been told they could die if they keep eating a certain way, or using a certain substance, and still they refuse to change, despite test results and scientific evidence.”

Dr. Nathan Wei, a Frederick, Maryland, board-certified rheumatologist with more than 30 years of practice and clinical research experience, agreed. He said it’s common for patients with lung cancer, even, to continue smoking.

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“However, let’s suppose a parent dies of lung cancer. Then, it’s not that uncommon for the children to adopt a no-smoking policy. Also, a parent may be a gun advocate, but if her child dies from a self-inflicted gunshot, she might change her mind.”

In his own practice, Wei says he’s had patients who were anti-pharma.

“But when they had an amazing recovery from their rheumatoid arthritis because of a new biologic therapy, they seemed to have a change of heart,” he said.

It can take a lot for a patient to get to that point, however, which is why Wei emphasizes how dangerous confirmation bias can be for a patient.

One patient with an inherent distrust of doctors developed a medical problem, but refused to seek treatment because of his beliefs. Wei said this individual was eventually persuaded to go to the doctor, but by that time the damage was done.

“The destruction that had occurred in the joints as well as the heart couldn’t be reversed — all that could be done was to halt the disease where it was,” he said.

Wei and others theorize it might be the constantly changing influx of health information that makes it hard for people to embrace new research.

Dr. Murray Grossan, of the Grossan Science and Health Institute in Los Angeles, said vaccinations were once thought to cause mental changes; as a result, many parents didn’t get their children vaccinated. However, those kids developed measles, which had serious consequences.

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“I remember a patient from a wealthy family who became deaf after contracting measles as a result of not being vaccinated,” Grossan said, adding the patient isn’t always to blame.

He said that chocolate, meat and eggs were all placed on the “bad” list at some point, and are now they’re on the “good” list. Offering another example of changing information, he said a patient goes to the doctor complaining of shoulder pain. The doctor advises him to put heat on it. The patient goes to another doctor, who recommends putting a cold pack on it.

“If the patient comes to me, I’ll tell him to leave the shoulder alone,” he said.

Another study found that people in Los Angeles who lived under a flight path were subject to mental illness and addiction, so it was concluded that living under the flight path must be harmful to your health. Grossan pointed out however, that the higher than normal levels of mental illness and addiction were actually because the people in the survey lived in motels for transients.

“Today we are beginning to find that many studies were not so scientific and have to be retracted,” Grossan said.

Health consumer, beware — and perhaps even be ready to admit you were wrong. That new conclusion could lead to better outcomes for your overall health.