When Is A Placebo Not A Placebo?

Irving Kirsch, best known for that 2008 meta-analysis allegedly showing that "Prozac doesn't work", has hit the headlines again.

This time it's a paper claiming that something does work. Actually Kirsch is only a minor author on the paper by Kaptchuck et al: Placebos without Deception.

In essence, they asked whether a placebo treatment - a dummy pill with no active ingredients - works even if you know that it's a placebo. Conventional wisdom would say no, because the placebo effect is driven by the patient's belief in the effectiveness of the pill.

Kaptchuck et al took 80 patients with Irritable Bowel Syndrome (IBS) and recruited them into a trial of "a novel mind-body management study of IBS". Half of the patients got no treatment at all. The other half got inert cellulose capsules, after having been told, truthfully, that the pills contained no active drugs but also having been told to expect improvement in a 15 minute briefing session on the grounds that

placebo pills, something like sugar pills, have been shown in rigorous clinical testing to produce significant mind-body self-healing processes.

Guess what? The placebo group did better than the no treatment group, or at least they reported that they did (all the outcomes were subjective). The article has been much blogged about, and you should read those posts for a more detailed and in some cases skeptical examination, but really, this is entirely unsurprising and doesn't challenge the conventional wisdom about placebos.

The folks in this trial believed in the possibility that the pills would make them feel better. They just wouldn't have agreed to take part otherwise. And when those people got the treatment that they expected to work, they felt better. That's just the plain old placebo effect. We already know that the placebo effect is very strong in IBS, a disease which is, at least in many cases, psychosomatic.

So the only really new result here is that there are people out there who'll believe that they'll experience improvement from sugar pills, if you give them a 15 minute briefing about the "mind-body self-healing" properties of those pills. That's an interesting addition to the record of human quirkiness, but it doesn't really tell us anything new about placebos.

Kaptchuk, T., Friedlander, E., Kelley, J., Sanchez, M., Kokkotou, E., Singer, J., Kowalczykowski, M., Miller, F., Kirsch, I., & Lembo, A. (2010). Placebos without Deception: A Randomized Controlled Trial in Irritable Bowel Syndrome PLoS ONE, 5 (12) DOI: 10.1371/journal.pone.0015591