Most patients, confronted with an illness, ask the question, “Why? Why now?” or, even more anxiously, “Why me?”
Despite these questions, they may already have arrived at their own theory of causation, very often involving temporal sequence. When something especially beneficial or harmful occurs, we want to know what caused it.
There is the idea that any event which happened first must be the particular event that caused a good or bad event later.
Often it seems absolutely clear that a specific action caused a second event to happen. It is logical enough … but only on the surface.
Correlation and causation are often confused because the human mind likes to find patterns even when they do not exist. We often fabricate these patterns when two variables appear to be so closely associated that one must be dependent on the other. That would imply a cause and effect relationship where the dependent event is, after all, considered as the result of an independent event.
Correlation and causation
Correlation is different from causation; correlation does not imply causation although they can exist at the same time. There is correlation when two or more things or events tend to occur at about the same time and might be associated with each other but are not necessarily connected by a cause/effect relationship. When there is a cause/effect relationship, there is causation.
We get into trouble when the mind seeks or creates an artificial cause/effect relationship that does not actually exist. We tend to focus on the first action we noticed before the effect, then assume that it must have been what triggered the later event. Nine times out of 10, we are right, but we forget that one time out of 10 we pick the wrong cause.
What does all of this mean for doctors? When doctors diagnose disease, they are inevitably involved in questions of cause and effect. Patients cannot be treated effectively if the clinicians do not clearly understand pathogenesis and etiology, that is, causation.
When searching for the etiology of disease, sometimes doctors cannot assign an ultimate cause, which is extremely unsatisfying both for them and for the patients.
Establishing a cause
The search for cause, among doctors and patients alike, is in some sense a search for control.
The whole concept of luck, good or bad, is alien to the medical enterprise.
Doctors, like their patients, want to know why. They want to get to the bottom of the puzzle, they need to know the cause so they can treat, cure, prevent, or eradicate a disease.
They need to work on it together, as a team. Even more when causes are complex and outcomes uncertain.
Establishing a definitive cause can be difficult as correlation does not imply causation. Events or statistics that happen to coincide with each other are not necessarily causally related. The reality is that cause and effect can be indirect and due to a third factor, or entirely coincidental. The assumption of causation is false when the only evidence available is simple correlation.
Distinguishing correlation from cause depends on the quality of the evidence and the strength of the association.
The search for cause is a serious enterprise because falsely assigning a cause can do significant harm.
Some years ago, a Hungarian medical study of 221 men who carried cell phones found that men who carry cell phones in the front pockets of their trousers rather than in a jacket or briefcase had a 30% lower sperm count than the average male population as previously measured in 1970. Immediately an outcry appeared to start lawsuits against cell phone companies for causing sterility in men, and some consumer watchdogs called for warning labels on cell phones.
The problem is that the study only found correlations, it did not determine clear causation. As it was pointed out later, many individuals who carry their cell phones in their trouser pockets rather than their jacket pockets, do so because they are smokers. They carry their cigarette pack in their jacket pockets instead of their trouser pockets, to avoid crushing their cigarettes and thus must carry the cellphone in their trousers instead.
It has long been known that smokers have a reduced sperm count. Perhaps smoking caused the lower sperm count rather than the position of the cell phone per se. Finally, the overall sperm count of men may have dropped locally or globally, possibly due to the increasing levels of chemical pollution worldwide. Male alligators in parts of Florida, for example, also have lower sperm counts than they usually did, but nobody thinks that it is a result of their cell phone use!
However, the least you can do is pause and ask yourself what other possible causes exist in addition to the apparently obvious one.
Why? Why me? Why now?
For patients, these are important questions and doctors must help them to find the answers; the most accurate possible answers, even if these answers might not be the ones expected or desired.
Best health wishes,
Dr Maria Alice is a consultant in General and Family Medicine. General Manager/Medical Director – Luzdoc International Medical Service. Medical Director – Grupo Hospital Particular do Algarve/ Hospital S. Gonçalo de Lagos