Placebo quirks

I was reading a book the other day (Cracked: Why Psychiatry is Doing More Harm Than Good, by James Davies) about modern ‘medical’ (or drug) psychiatry. In it he mentioned an interesting quirk about side-effects and the placebo response that I hadn’t been aware of.

He was writing about how – in the case of anti-depressants – there is only a small additional benefit over and above placebo conferred by taking the drug. In fact, this extra benefit is typically just a few points on the 51 point Hamilton Scale (a standard before and after test often used in trials in this area). So the more substantial proportion of the total benefit is indeed the placebo effect.

But then he went on to mention how some of that additional benefit that the drugs have relative to placebo might be a quirk of the side-effects of the drugs.

It goes like this. All enrolled in the trial are told that¬†they might be on the active drug, or might be on a placebo. Participants are informed of likely side-effects from the medicine. In other words, that they might get side-effects IF they are allocated to the ‘real’ group.

Now, if someone is allocated to the drug (but does not know) then IF they get a side-effect, they then might well think “Hang on! That must mean I’m on the active drug?”. Knowing this might well generate an incremental placebo benefit compared to not knowing.

Now, of course, some people NOT on the active drug might develop side-effects similar to the drug side-effects (either for independent reasons such as getting a dry mouth if they have a cold, or as an active placebo – actually nocebo – type response itself).

But it is reasonable to assume that this latter effect will be smaller than the former, and the difference between the two will presumably be more the stronger and more diverse the side-effects of the active drug!

So some of the performance (already rather small) claimed by big pharma may be somewhat illusory.

I wonder whether we bump into this with patients? “You might develop a reaction to treatment if we have done the right thing today and got those stiff segments moving…”. Or some such.

The placebo is quite a slippery thing.

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