See also this article by Steve Silberman.
One problem I had when reading Silberman is that there was some vagueness around what the "placebo effect" was supposed to be. He was constantly referring to it as if it were a real thing, but that struck me as a figure-ground inversion: a controlled experiment doesn't "measure the placebo effect", it tries to accurately measure the effect of the drug's active ingredient by keeping every other effect the same (i.e. identically distributed). (Things cleared up a little for me when I read Peter Lipson's response to Silberman, though his critique also has some vagueness to it.)
So what "the placebo effect" really means is "every random effect other than that of the active ingredient". It does not mean "the beneficial effects of taking a pill that you think is going to help even though it contains no active ingredient", even though that's the meaning implied by these articles.
The linked article is different in an interesting way. The study referenced measured the difference between a "no treatment" group (i.e. no pill but the same interaction with doctors) and a group receiving treatment consisting of an avowedly inactive pill patients were told would help through "psychological effects".
One problem I can see is that the instrument used to measure "effects" of the "placebo" is itself psychological: the IBS-GIS as far as I can tell is a questionnaire given to the patients. So quite possibly this study is replicating priming effects, not necessarily measuring actual difference in health outcomes.
I agree with your skepticism about relying on self-reports for a measure. But what do you mean by, "priming effects"?
I hope you mean disturbing in a good way, as in "I am committed to understanding the world, not finding evidence to support my view of how I want the world to look." I knowingly use the placebo effect on myself, relieving all sorts of things with ibuprofen. I figure the little bit of real pain relief the ibuprofen provides probably helps me to imagine myself better in other ways after I take it.
Perhaps the placebo effect works even when you know it is a sugar pill in the same way that essentially all optical illusions work even though we know they are illusions. Placebo effect probably reflects some deep wiring in us, which would hardly be expected to go away just because we know about it.
A possible defect in the study: it was based on people reporting improvement. That my knowing I took a fake pill might get me to report a fake improvement I don't think should be ruled out. I think I would like to see if Placebos can lower temperature in a fever, and compare the effectiveness of placebos when we tell you its a placebo and placebos given in all seriousness as an implied effective drug.
An acquaintance regularly treats headaches by putting two aspirins in his shirt pocket.
He is as bemused by this as anyone, but figures as long as the headache goes away, why should he actually consume the aspirin?
I can't fault his reasoning, though I'll admit to finding it disturbing.
I wonder how far he can take it.
If he can't find aspirin, can he write "aspirin" on a piece of paper and put that in his pocket? Can he just imagine doing it? Or can he do absolutely nothing and have it still go away?
Regarding writing it on a piece of paper: apparently some homeopaths actually do that. (And this is regarded by mainstream homeopaths as superstitious pseudoscience.)
Well it's obviously not homeopathy, since you can clearly distinguish between a piece of paper saying "homeopathic remedy" and a piece of paper saying "ordinary water".
What they need to do is write "homeopathic remedy" on some paper, pulp it with clean paper in a 1/1,000,000 proportion, make recycled paper out of it, and give the patient some of that recycled paper. Without writing anything on it.
I've wondered that myself, though I've never asked. I expect he could train himself to eliminate the headaches without the ritual, were he inclined to do so.
Ibuprofen isn't exactly a trivial pain reliever; it's decidedly more effective than tylenol and about the same effectiveness as codeine.
May be true on average, but YMMV. I find it slightly less effective than paracetamol (Tylenol) and way less than codeine. (I have a dodgy back and a keen interest in painkillers at times.)
Codeine is almost always mixed with tylenol or another painkiller, and in its mixed form is more effective than pure codeine or ibuprofen. I meant that pure codeine is about as ibuprofen (not by weight, but by equivalent dosages) but it's not really a useful comparison because pure codeine is rarely prescribed.
The effect size is 1.6 sigma; 80 people, 40 in each group, 24 versus 14 improvements. The null hypothesis is by no means ruled out. That's in addition to the double-blinding problems others have noted.
I wish they had included a third group which received a placebo and was told it was real medicine. The study's not properly complete without one.
I'm not particularly surprised by the results, but I'd be very surprised if the people who knowingly take a placebo do as well as the people who take a placebo believing it's real medicine.
I wish they had included a third group which received a placebo and was told it was real medicine.
That's pretty much what I meant by "... third group who received a placebo that they didn't know was a placebo".
It can work, but it's not an at-will magic spell, unfortunately. And it seems you gotta be a special kind of wizard to use the effect. If anyone knows how to reliably manifest I'll gladly apprentice under them. There's nothing that makes me think people who think hereustics and biases is a useful paradigm more than the existence of placebos. Magical thinking, while a 'bias', literally works and is useful. Anticipation is itself an effective mental magic trick. Here's a summary of the most evidence I've found:
"]) Roughly only 30% of the population seems susceptible to placebo effects, and it is not possible to determine ahead of time whether a placebo will work or not. (However the placebo effect is zero in studies of blood poisoning and up to 80% in studies of wound on the duodenum). Patients rightfully want immediate relief or improvement from their illness or symptoms. A non-placebo can often provide that, while a placebo might not. Legitimate doctors and pharmacists could open themselves up to charges of fraud since sugar pills would cost pennies or cents for a bottle, but the price for a “real” medication would have to be charged to avoid making the patient suspicious. - Google Search
The desire for relief from pain, “goal motivation”, and how far pain is expected to be relieved increases placebo analgesia.[82] Another factor increasing the effectiveness of placebos is the degree to which a person attends to their symptoms, “somatic focus”.[83] Individual variation in response to analgesic placebos has been linked to regional neurochemical differences in the internal affective state of the individuals experiencing pain.[140]Those with Alzheimer’s disease lose the capacity to be influenced by placebos, and this is attributed to the loss of their prefrontal cortex dependent capacity to have expectations.[141] - Google Search
Mechanism of the effectA 2001 meta-analysis of clinical trials with placebo groups and no-treatment groups found no evidence for a placebo effect on objectively measured outcomes and possible small benefits in studies with continuous subjective outcomes (particularly pain).[16] A 2004 follow-up analysis found similar results and increased evidence of bias in smaller trials that calls into question the apparent placebo effect on subjective outcomes.[42]Because the placebo response is simply the patient response that cannot be attributed to an investigational intervention, there are multiple possible components of a measured placebo effect. These components have varying relevance depending on study design and the types of observations.[43] While there is some evidence that placebo interventions can alter levels of hormones[44] or endogenous opioids,[45] other prominent components include expectancy effects, regression to the mean,[46][47] and flawed research methodologies. - Google Search
Since the publication of Henry K. Beecher’s The Powerful Placebo[15] in 1955, the phenomenon has been considered to have clinically important effects.[16] This view was notably challenged when, in 2001, a systematic review of clinical trials concluded that there was no evidence of clinically important effects, except perhaps in the treatment of pain and continuous subjective outcomes.[16] The article received a flurry of criticism,[17] but the authors later published a Cochrane review with similar conclusions (updated as of 2010).[18] Most studies have attributed the difference from baseline until the end of the trial to a placebo effect, but the reviewers examined studies which had both placebo and untreated groups in order to distinguish the placebo effect from the natural progression of the disease.[16] - Google Search
Motivation may contribute to the placebo effect. The active goals of an individual changes his/her somatic experience by altering the detection and interpretation of expectation-congruent symptoms, and by changing the behavioral strategies a person pursues.[82][83] Motivation may link to the meaning through which people experience illness and treatment. Such meaning is derived from the culture in which they live and which informs them about the nature of illness and how it responds to treatment. Research into the placebo treatment of gastric and duodenal ulcers shows that this varies widely with society.[17] The placebo effect in treating gastric ulcers is low in Brazil, higher in northern Europe (Denmark, Netherlands), and extremely high in Germany. However, the placebo effect in treating hypertension is lower in Germany than elsewhere.[84] Social observation can induce a placebo effect such when a person sees another having reduced pain following what they believe is a pain reducing procedure.[85] - Google Search
See also this article by Steve Silberman.
One problem I had when reading Silberman is that there was some vagueness around what the "placebo effect" was supposed to be. He was constantly referring to it as if it were a real thing, but that struck me as a figure-ground inversion: a controlled experiment doesn't "measure the placebo effect", it tries to accurately measure the effect of the drug's active ingredient by keeping every other effect the same (i.e. identically distributed). (Things cleared up a little for me when I read Peter Lipson's response to Silberman, though his critique also has some vagueness to it.)
So what "the placebo effect" really means is "every random effect other than that of the active ingredient". It does not mean "the beneficial effects of taking a pill that you think is going to help even though it contains no active ingredient", even though that's the meaning implied by these articles.
The linked article is different in an interesting way. The study referenced measured the difference between a "no treatment" group (i.e. no pill but the same interaction with doctors) and a group receiving treatment consisting of an avowedly inactive pill patients were told would help through "psychological effects".
One problem I can see is that the instrument used to measure "effects" of the "placebo" is itself psychological: the IBS-GIS as far as I can tell is a questionnaire given to the patients. So quite possibly this study is replicating priming effects, not necessarily measuring actual difference in health outcomes.
I agree with your skepticism about relying on self-reports for a measure. But what do you mean by, "priming effects"?
Placebo Effect Benefits Patients Even When They Knowingly Take a Fake Pill
This is a little bit disturbing. (A kind of belief in belief, perhaps? Like, "I know a placebo is where you take a fake pill but it makes you feel better anyway if you believe it's real medicine, so I'd better believe this is real medicine!")
Though it's too bad they (apparently) didn't have a third group who received a placebo that they didn't know was a placebo, to compare the effect size.
Edit: Here's the actual study. RolfAndreassen points out that its results may not actually be strong evidence for what is being claimed.