Date: 11/07/2020
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Lower Back Pain and the Placebo Effect

Low back pain is a condition so common that, intermittently, I suffer from it myself. It comes and goes for no apparent reason, lasting a few days at a time. Nearly 40 years ago I realized that, though I had liked to think of myself as nearly immune from nervous tension, anxiety could cause it.

I was in a far distant country and I had a problem with my return air ticket. At the same time I suffered agonizing low back pain, which I did not connect with the problem of my ticket. When the problem was sorted out, however, my back pain disappeared within two hours.

In general, low back pain is poorly correlated with X-ray and MRI findings. Epidemiological research shows that the self-employed are much less prone to it than employees, and also that those higher in the hierarchy suffer it less than those lower – and not because they do less physical labor. Now comes evidence, in a recent paper from Australia published in the Lancet, that the recommended first treatment usually given for such pain, acetaminophen, also known as paracetamol, is useless, or at least no better than placebo (which is not quite the same thing, of course).

The Australian authors designed a double-blind trial for people with low back pain. The first group was given the drug regularly, up to the maximum safe daily dose; the second group was given it to take as and when they felt it necessary, up to the maximum safe daily dose; and the third group was given a placebo, made to look exactly the same as the supposedly active drug, to take regularly. There were about 550 patients in each group, whose initial characteristics were very similar.

The end-point of the trial was seven successive pain-free days. It was supposed initially that the drug would be helpful because pain relief would promote the movement of the back muscles that is thought to promote recovery.

The results surprised me because in the past I had sometimes (though not always) had relief from the drug. It seems that I was mistaken and that, like the rest of mankind, I was susceptible to the placebo effect. The median time to recovery of the first group was 17 days; that of the second, 17 days; and that of the third, 16 days. In other words, the drug was of no use at all in shortening the duration of the pain.

But what about its severity and the consequent disturbance of function? When I have low back pain I am much slowed down in my daily life. Here again the drug was quite without beneficial effect compared with placebo. At no time in the treatment, and in no respect, was the active treatment better than placebo. The conclusion of the authors was categorical:

Paracetemol… had no effect on pain, disability, function, global symptom change, sleep, or quality of life.

But this conclusion was not quite justified; strictly speaking, it would have to be shown that the placebo effect did not improve low back pain, for only in this way could it be shown that the drug had no effect on low back pain. An experiment to demonstrate that a tablet given as a placebo had no placebo effect would be difficult to conduct, both for practical and ethical reasons.

I know that my low back pain is caused, at least in part, by anxiety. I know (now) that paracetamol (acetaminophen) has only a placebo if any effect at all. But I shall still take it whenever I have low back pain. So much for being a rational man.

First published in PJ Media.