Case-Control Studies

Case-control studies have led to some important discoveries. One of the most famous is the association between tobacco and lung cancer. Because they are relatively inexpensive and simple to conduct, they are very popular. However, you should be very cautious about accepting their results as fact until they are confirmed by more rigorous studies. Not infrequently, the results of a case-control study cannot be confirmed and may even be proven completely wrong.

When Are They Used?

Case-control studies are often used to identify possible causes or risk factors for a disease, condition or event. If a strong association can be found between a particular factor and the studied outcome, it may be the first step to identifying a previously unrecognized cause or risk factor.

What Is Their Biggest Problem?

There is no way to know if you have taken into account all the possible causes or risk factors for a given outcome. If the true cause is overlooked, something related to that cause (but not the outcome itself) may be mistakenly identified as an important factor. Thus, case-control studies can show an association between two things, but they can’t generally prove that one causes the other.

An Example:

Suppose we have two toxins, toxin A and toxin B. Let us suppose that they both are produced by the same process and thus are linked. Let’s also say that toxin A causes cancer C, but toxin B does not.

Suppose that while looking for a cause for cancer C, researchers found a strong link between toxin B and cancer C. If they didn't realize that there was a link between toxin A and toxin B (or cancer C), they might incorrectly conclude that toxin B causes cancer C.