Fallacies of reification - the placebo effect

Verbal self-reports of pain sensations are especially susceptible to expectancy effects: if I think I'm getting a painkiller, I might well report less pain than I actually feel.

I don't doubt that this is a "real" effect but we still have to distinguish pain vs. suffering, the objective and subjective components; as the saying goes "pain is inevitable, suffering is optional". So, I readily grant that some suffering is manipulable through expectancy effects. But there might exist better, more effective ways to alleviate suffering.

To me this still doesn't justify, e.g. selling sugar at a hundred times its market price.

As for "injection has a larger effect than pills", for instance, I doubt the strength of the data. The Wikipedia entry on placebo references a single 1961 article for this assertion, and the article would be ideal for this purpose since it focuses on an objective outcome measure (systolic and diastolic pressure) rather than subjective pain assessment.

But the Wikipedia commentary falls straight into a classic mistake of statistical inference: it confuses a difference of significance between two groups (the injection and oral placebo groups) with a significant difference. The oral placebo didn't show a statistically significant effect and the injection group did: this doesn't mean that there is a statistically significant difference between the two groups.

The citation for "acupuncture has a stronger effect than a pill" is to a Kaptchuk study that measured self-reported pain levels, so to me it's only saying "there is a stronger expectancy effect from having needles stuck into you than from taking a pill", which isn't earthshaking. Tellingly, the objective outcome measures (e.g. grip strength) showed no significant differences - my arm may feel better with needle treatment but it doesnt work better.

I'm not finding a citation for the bitter vs sweet thing in a quick Google search.

It's been claimed that color matters, but the one literature review I've looked at found these effects "inconsistent" across the studies examined. The studies were of poor quality in general and measured different things so a meta-analysis is not possible. Annoyingly the review reports things that strike me as irrelevant such as "the perceived action of different coloured drugs" which basically consists of asking people what they think a red drug will be most effective for. To me this sounded like a desperate bid to convince readers that "research contributing to a better understanding of the effect of the colour of drugs is warranted", the conclusion of the abstract. Sigh.

There are a multitude of such effects listed in The Strange Powers of the Placebo Effect, which is a truly amazing video on the subject. Unfortunately, it doesn't dive into details and doesn't seem to have much in the way of citations. I would agree that the effects it describe cause problems for the argument in the article.

To add a bit more information, this book covers a number of studies on the placebo effect (since the citations are in the book, which I do not have access to now, I don't know where to find the original studies.) These studies indicate that the strength of the placebo effect also varies according to the color of the medicine, with different colored pills acting as more effective placebos for different ailments, and that the placebo effect can outweigh the actual effects of a drug (so that a small dose of vomit-inducing medicine could cause less vomiting than the control group, which received no medicine, if offered as an anti-nausea medicine.)

I think there are two slightly different definitions of 'placebo' here, what we might call the 'strong' and 'weak' placebo effects.

The weak placebo effect, the existence of which I don't think anyone denies, is that for phenomena which are largely mental in nature, in particular pain, the mere belief that treatment has happened is enough to ease symptoms.

The strong placebo effect, for which as far as I'm aware there is no evidence whatsoever, but which is the basis for much of so-called 'evidence-based medicine', is the claim that, for example, we have to compare new cancer drugs to a placebo because a placebo might cause some shrinkage of the tumour. This is, frankly, nonsense.

To quote, leave off the quotation marks and begin the line with a greater-than sign >.

Why does one care about this?

Illustrative of a common failure of rationality, with instrumental consequences such as buying sugar at ridiculous markups.

Does any of this undermine the need to use placebos

Nope.

or eliminate 'the placebo effect' as a shorthand of how experiments/trials can fail to show that their proponents would like them to show?

"Control response" would be a better shorthand (obviating the need for the derived term "nocebo"). Better yet, if you're criticizing an experimental design, would be to pinpoint the specific criticism to a mechanism: regression to the mean, natural course of the disease, measurement error, expectancy effect, and so on.

If and only if the 'placebo effect' is real, we should anticipate the existence of some mechanism for belief in treatment to lead to improved outcomes (e.g.).

A previous discussion about placebo effects between Morendil and I can be found here.

Interesting, I agree with what Morendil said in that previous conversation but rejected this post at the first line. I guess that's just due to the difference between "there is no such thing as the placebo effect" and my position of "the placebo effect as commonly understood is almost entirely bullshit".

You come to me, your doctor, with a complaint, say the common cold. I charge you a lot of money, write you a prescription for Phosphorus 6C, send you to the pharmacy where you spend a further silly amount of money on sugar with concentrations of phosphorus ten thousand times less than the allowable concentration of arsenic in drinking water.

Next week I ring you to ask how things are going. You believe that you're supposed to have improved. It would make you feel rather silly to have gone to all this trouble to get essentially the same result as your cold clearing up of its own accord. You would rather feel clever about your choice of doctors and your overall judgement. None of that is conscious, but it still plays a role in picking your verbal response. You say "Much improved, Doc, thanks! That thing you gave me worked wonders!"

In all other particulars - nasal secretions, immune response, number of sneezes, actual misery experienced - this episode has been identical to what would have transpired if, counterfactually, you had decided to "tough it" and allow the cold to run its course. (I may hedge my bets on the "actual misery experienced" measure, if there were a way to actually get a number for that; I think the first-order misery is the same, but possibly you feel better about feeling miserable, knowing that it's soon going to pass.)

The observation that animals modulate immune response depending on perceptual cues is interesting, but you have to cross a fair inferential distance before you get anywhere near "the placebo effect".

This crossing goes something like, "you're manipulating something (lighting conditions) that has an effect only via the animal's perceptions", so that in effect you are "making the animal believe it's winter" - and then arguing that "since the result of this is a modulation of the immune system, it must be the case that beliefs can have an effect on the immune system" - and from there we bridge the final gap to "therefore this might be how the placebo effect works, by using the same mechanism whereby beliefs influence the immune system".

This final gap is speculative. Even if the hypothesis were true, it would only explain a select few of the control responses observed in experimental trials, not all of them. And the hypothesis doesn't mean that things like regression to the mean, measurement error, expectancy effects and so on are not also playing a role in control responses - it's only one more mechanism that joins these others in confounding the results of experimental trials.

More importantly, we don't know that what happens in placebo-controlled studies is anything like that, and the article adduces precisely zero evidence for that hypothesis. We have no idea whether humans respond to anything of the sort, and even if that was the case we wouldn't necessarily be able to harness the effect for curative purposes.

On top of all which Hanson adds an extra bit of speculation - "evolution shaped us to interpret being cared for in the same way that we would interpret other cues, such as long days, that we are in a situation of abundant resources" - still with not a shred of evidence.

All this reminds me of Mark Twain's quip: “There is something fascinating about science. One gets such a wholesale return of conjecture out of a trifling investment of fact."

That's basically what I thought the article was doing.