Even Knowingly Taking A Placebo Seems To Help (2010)

This study seemed to deal with people experiencing digestion problems. I wonder if it was the act of drinking extra glasses of water (to swallow the placebos) that helped the situation, rather than the psychology here.

Well, now it's known that a placebo works, and the mind being mysterious still, a placebo is only a known unknown.

But if you give a sugar pill to a person who had never heard of the placebo effect, and tell him/her that the pill is only sugar with no effect whatsoever, perhaps we might find that the placebo effect does not manifest.

Exactly. And just being involved in a study, having the feeling of purpose...lots of variables.

The Placebo Effect is something of a misnomer, as there are actually many different placebo effects, which bias trial data in subtle and interesting ways. Effects like regression to the mean and the natural history of the disease, for example, will result in objective changes to a patient's condition even in cases where the patient is acutely aware they are only taking a placebo.

Analyses comparing placebo interventions to no treatment reveal that the apparent power of the placebo may be overstated. No placebo effects are observed, for example, when comparing placebo to no treatment for objective endpoints, or binary endpoints (Hróbjartsson et al, 2001). They are observed in subjective endpoints (e.g. pain, nausea) where the condition of the patient is filtered through the opinion and biases of the patient and/or the clinician - which makes it quite possible that this aspect of placebo action can be accounted for by the experimenter effect.

All of which leads to my primary problem with this paper. It is a comparison of open-label placebo to no treatment, with a relatively small number of participants (n = 80), studying only subjective end-points (hello, experimenter effect). The media coverage of this paper (c.f. the NPR article) makes the claim that an "honest placebo" was given, with the patients informed they were only taking placebo, which is true. But patients were also told the placebo could "present significant improvement in IBS symptoms through mind-body self-healing processes", which just as readily primes the patient for the experimenter effect as does telling them they're taking a drug.

On top of that, the clinical relevance of the IBS-GIS improvement seen in the placebo arm is questionable, improvement from "(4) no change" to "(5) slight improvement" on a seven point scale.

Small effect, small numbers, and potentially flawed methodology.

>with respect to the drinking of water, that's unlikely...

With my reading, taking water - in gulps to wash down the pill - at particular times/regularity could be a/the significant factor getting measured in this study. Perhaps there is a threshold effect in taking the water (e.g: it helps people on the threshold of dehydration), or perhaps it's the time of day taken. I may be wrong, but I don't think it should just be summarily dismissed yet.