Last reviewed and revised February 27, 2013
As a retired doctor, my father used to tell me about one of his patients who blamed his doctors for his ills. "I was fine before I came to see you but by the end of my first visit, I had high blood pressure and high cholesterol. What are you doing to me?" His patient was kidding — at least I think he was — but it's an example of how reasoning can go wrong when an initial event is assumed to cause something that occurs soon afterward. On the other hand, my father used to joke that his children (especially me) were the cause of his gray hair. As improbable as it was that my father was the cause of his patient's elevated blood pressure, similar faulty assumptions are the basis of many medical myths.
I have heard from patients who have diabetes that they would rather avoid taking insulin because they fear it will hasten complications such as amputation of limbs or kidney failure. Never mind that doctors would never knowingly prescribe a medication with a complication rate that exceeds its benefits, but most research suggests that if there's any long-term effect of careful blood-sugar control in diabetes — which often requires insulin — it is to reduce the risk of complications.
Why would such a myth be so persistent? It is probably based on experience with family or friends who took insulin for their diabetes and later developed these complications. It is certainly true that people with diabetes may have significant problems with circulation that may slow wound healing. And non-healing or infected wounds sometimes require amputation of the involved limb, but this is more common among those with the more severe deficiency of insulin, not just resistance to it. And it is these more severe cases (called type 1 when the problem is lack of insulin in the body) that require insulin therapy, often years before the complications develop.
So, although the insulin comes first for many patients with diabetes, it is the disease for which insulin is required — and not the insulin itself — that increases the risk of complications. Unfortunately, avoiding insulin therapy because of the mistaken assumption that it may cause complications actually could increase the risk of those same complications.
You twist your ankle and now it's sore. The cause and the effect are straightforward, but in many (or even most) medical situations, a number of factors may complicate matters:
In making health care decisions, as in so many other situations, we all should do our best to avoid making assumptions and drawing quick conclusions. Doing so may lead to unwise choices. Tell your health care professional your concerns about your health, your medications or any medical recommendations made to you. If your concerns are based on inaccurate or incomplete information, setting the record straight could improve your understanding of your health and any illnesses you have. More important, you may even improve your health by changing your mind about a health decision you have made.
For example, if smokers are found to have high blood pressure (hypertension) more often than non-smokers, smoking may be assumed to be the cause. (In fact, nicotine can raise blood pressure. However, if smokers are also overweight more often than non-smokers, one must account for weight before attributing the cause of blood pressure problems solely to smoking. Weight is a "confounder" is this example because it can cause the same effect as the factor assumed to be causal (smoking); confounding is an important source of error in medical research.It is likely that many important factors that contribute to disease have not yet been discovered and therefore cannot be specifically accounted for in research – until their importance is recognized, these factors could be confounding research and confusing conclusions about cause and effect. Meanwhile, the assumptions of cause and effect are in error. Smoking cessation and loss of excess weight are both recommended for people who have hypertension.
And if I practice what I preach, maybe I'll stop blaming my kids for my graying hair.
Robert H. Shmerling, M.D., is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.