Common and Normal
Quick Summary: Normal refers to typical, while common is related to prevalence. While some things are both common and normal, many times we incorrectly assume that because something is common, it is also normal.
Concepts that are superficially similar, but actually quite different, are often confused. For example, one of the first emails I wrote was on the difference between simple and easy. Separating similar topics often helps us clarify our thinking; disentangling related concepts often brings clarity to the challenges we face.
With that in mind, this article focuses on two related concepts: common and normal. Patients frequently ask me Is this normal? and my response if often It is common. It is not normal. What’s the difference? And why is it important to be clear about the difference?
Normal refers to something that conforms to a standard, something that is expected or typical. Common, on the other hand, means something that is prevalent, something that occurs frequently. While these definitions may seem similar, they have distinct differences.
For example, it’s common for people to experience joint pain as they age, but that doesn’t necessarily mean it’s normal. Normal joint function involves minimal pain, discomfort, and proper movement. So while joint pain may be common, particularly as we age, it’s not normal.
Another example is high blood pressure, which is common in older adults, but not normal. High blood pressure can lead to a host of health issues such as heart disease, stroke, and kidney damage. There was a time in medicine when there was debate about this– is elevated blood pressure a normal part of aging, or is it more common as we age? It turns out, it is more common as we age, but elevated blood pressure in your 60s or 70s still predisposes you to cardiovascular disease, and lowering it decreases risk.
So, while something may be common, it’s not always normal. Why do we confuse these? Probably, the answer lies in our tendency to accept the status quo and to generalize from the world around us. We often assume that what we are accustomed to is normal, and so do not question it. If you are 70, and most of the people you know have high blood pressure, you might assume it is normal– rather than common.
Things that are normal are not necessarily common either. Because of our tendency to generalize from our own experience, we might assume that it is normal to live to be 70 or 80, because it is now common. However, this is historically not normal, and not common. Eating food that has been produced in a factory is now common, but I would argue is not normal.
Don’t assume that just because something is common, it’s normal. Where do you confuse these ideas? Can you think of something you’ve always dismissed as normal that is, in fact, common but abnormal?

-Dr. Justin