Dr David McGrath

Spine Physician

MB BS (Hons) FAFOM, RACP, FAFMM
Master of Pain Medicine

Cause and Effect (Part 2) (Convergence of Positive/Negative factors)

In part one we concluded, that mere association is not sufficient to deduce cause and effect.

We need to reach the conclusion, that without event A, event C could NOT have occured. Under these conditions, A is a cause of C.

There may be other causes as well. We might discover Essential Convergence. That is,without B, C could also not have occured. In other words, A+B are necessary for C.
When we have essential convergence, such as this, we can only state, we have discovered a cause A. We cannot know all of the other co-factors in a convergence arrangement.

To generalise A+B+D+E+F.....=C All of factors A,B,D,.. are legitimately causes under the criteria, that they are needed.

For example
1. If I fall over a bucket and hurt myself, I could state that the bucket (A) is THE cause. This is incorrect. The bucket is "A "cause. There are other essential factors, such as poor lighting (B), my drunken state (D),and my poor balance (E)
To complicate matters, some of the factors A,B,D.. could be historical factors. My poor balance may be due to an incomplete healing of a sprained ankle, ten years ealier.
The juxtaposition of historical and contemporary factors in convergent cause, is a common cause of confusion and conflict in medicolegal situations.
2. A heart attack, may be due to recent stress and established heart disease, created by historical factors.

There is also the unfortunate possibility, that there are multiple sets of causes, for the one identifiable phenomena. That is, there are separate convergent causal sets.

To generalize A+B+C...=C and D+E+F....=C

For example
1. Low back pain might be caused by, an old healed fracture, recent loss of spinal fitness, and an acute wrench.
2. Low back pain pain may also be due to, vitamin deficiency, scoliosis and recent exercise.

Now it is quite possible, that the two types of low back pain (LBP) are distinguishable, in which case, we could focus on the individual factors of each set. If they are not,we will struggle with many factors or interventions which are irrelevent. The more vague the identifiable phenomena or disease, the worse the situation.
On the other hand, the more precise the diagnosis, the greater the chance that that there are only a few causal sets, with limited numbers of convergent inputs.
If the diagnosis is isolated disc disease. (diagnosed by modern imaging), the most likely cause is a traumatic frature to the vertebral end plate (VEP) leadind to poor disc nutrition, death of chondrocytes, loss of disc core matrix and so on,to painful dynamics. Even with this specificity,further factors, such as nutrition and lifestyle are likely to be important, in the final expression of pain.

(to be continued)