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Placebo Quirks

a photo of some pills on a table

This should be interesting if you, like me, are fascinated by how the mind influences the body.

I was reading a book the other day about modern psychiatry.

Cracked: Why Psychiatry is Doing More Harm Than Good, by James Davies

Well known is that for antidepressants there’s a relatively small additional benefit over and above placebo gained by taking the drug.

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 biggest proportion of the total benefit is the placebo effect.

Less well known is that, oddly, some of this additional benefit the drug has relative to a placebo might be a quirk of the side-effects of the drug.

It goes like this.

All enrolled in the trial are told that they might be on the active drug or on a placebo. Ethically, participants need to be informed of likely side-effects from the medicine. In other words, that they might get side-effects if they are allocated to the active drug group.

Now, if they are allocated to the active group, and get a side-effect, they then think, that must mean I’m on the active drug.

Believing this might generate an incremental placebo benefit.

Offsetting this effect, some in the placebo group may develop side-effects. For example, they might just get a cold and develop a dry mouth. Or they might worry that they are in the active group – a nocebo response.

But it seems reasonable to assume that this latter effect will be smaller than the former.

The net effect is that the drug gets a small artificial boost to its effectiveness.

The placebo is a weird thing.

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