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The Placebo Effect

Because when we use placebo controls, they are one of the things that's being controlled for.
The control is being controlled for? :confused:

We also know that the effect "people experience social pressure to say the medicine makes them feel better" is a real effect that can be controlled for (we control for it using placebos), that doesn't mean it's not part of the placebo effect.

Every aspect of the placebo effect can at least potentially be known and controlled for. Why would that make them not placebo?
You're confusing me. Now you're saying there's no placebo effect because everything can be controlled for.
 
Arth said:
The fact that we can potentially track down the different aspects of placebo doesn't make them not placebo.
Why would they be? If they are known and can be controlled for, why are they still placebo? That doesn't make sense.
Because when we use placebo controls, they are one of the things that's being controlled for.

"They" are the actual effects we're talking about. We control for those effects in placebo controlled trials. The reason we give people placebos is to control for a variety of effects. To the extent that an actual physiological mechanism exists, that will be one of the effects that's being controlled for.
 
You're confusing me. Now you're saying there's no placebo effect because everything can be controlled for.

Maybe that's the implication of your weird definition of placebo, but it's clearly not the implication of my view.

One more time: We do placebo controlled trials for a reason. The reason is to control for a variety of effects. Every one of those effects is a part of the placebo effect. The fact that we understand some of those things doesn't make them not a part of the placebo effect.

We understand for instance that sometimes people taking medication expect to feel better, and thus are more alert to improvements in their condition so are more likely to report positive improvements than those receiving no treatment. That's part of the placebo effect. The fact that we understand the mechanism doesn't make it not part of the placebo effect. The fact that we can control for it by giving people sugar pills doesn't make it not part of the placebo effect.
 
But to be clear, when you say that the placebo effect is a sham, you aren't saying that such effects don't exist?
To be clear, I'm saying, and always have been saying since the very first post in the thread, that the so-called "Powerful Placebo" effect - the "mind over matter" effect that Kapchuk and others promote - is a sham.

In the most recent set of conversations I have been saying that the media claiming that we now understand and can control the placebo effect is wrong. One potential mechanism of placebo has been identified. That doesn't explain the whole placebo effect.
 
We understand for instance that sometimes people taking medication expect to feel better, and thus are more alert to improvements in their condition so are more likely to report positive improvements than those receiving no treatment. That's part of the placebo effect. The fact that we understand the mechanism doesn't make it not part of the placebo effect. The fact that we can control for it by giving people sugar pills doesn't make it not part of the placebo effect.
If you control for, say, regression to the mean in your clinical trial, then regression to the mean no longer contributes to the placebo effect in that trial. That doesn't mean that it is never a placebo factor, but it does mean that it doesn't count towards the placebo effect in your trial. That's why controls exist - to eliminate factors that could otherwise contribute to a placebo effect in your trial.

Is this a clearer way of putting it?
 
If they are known and can be controlled for, why are they still placebo? That doesn't make sense.


You're very confused. Placebo effects are precisely what placebo-controlled trials control. Whether we know the mechanism of the effect or not is irrelevant.
 
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You're very confused. Placebo effects are precisely what placebo-controlled trials are designed to control. Whether we know the mechanism of the effect or not is irrelevant.
Which is why I say that the mouse study shouldn't be considered as addressing the placebo effect at all.
 
I'm a bit confused as to why when something is known and controlled, it somehow is still part of a placebo effect. The placebo effect is defined as all of the responses that are not controlled for.


This appears to be the source of your confusion. Your definition of placebo effect is wrong. The placebo effect is all responses that are not due to the active treatment. Consider the case of a pill comprised of an active ingredient in an inert medium. The placebo effect is any effect not due to the active ingredient. In principle, if you treat the active treatment arm and the placebo arm of a trial identically except that you give the placebo arm the pill minus the active ingredient, then you have controlled for all placebo effects (regardless of any knowledge you may have about their mechanisms).
 
In principle, if you treat the active treatment arm and the placebo arm of a trial identically except that you give the placebo arm the pill minus the active ingredient, then you have controlled for all placebo effects (regardless of any knowledge you may have about their mechanisms).
In a "spherical cow in a vacuum" sense yes. But that doesn't mean that all these effects are one thing that one interesting experiment can explain, in the way that the reporting suggests that the mouse study explains them.
 
In a "spherical cow in a vacuum" sense yes.


I have no idea what that means.

But that doesn't mean that all these effects are one thing that one interesting experiment can explain, in the way that the reporting suggests that the mouse study explains them.


I haven't read about the mouse study you are referring to, and it doesn't matter. What I am telling you is that you don't understand what is meant in medicine by "placebo effect."
 
The misconceptions you have expressed about what the placebo effect is, which I have corrected you on, are misconceptions, period. They do not depend on what some mouse study may or may not have to say.
What I have been saying (recently) about the placebo effect are in direct reference to the mouse study referenced in this post.
 
What you wrote was wrong in any context.

You wrote:

"The placebo effect is defined as all of the responses that are not controlled for."

That is wrong.

You wrote:

"If you control for, say, regression to the mean in your clinical trial, then regression to the mean no longer contributes to the placebo effect in that trial."

That is worse than wrong. It is nonsense because regression to the mean is not a placebo effect.

You wrote:

"That doesn't mean that it [regression to the mean] is never a placebo factor..."

Regression to the mean is never a placebo effect, and a placebo, therefore, never controls it.

You wrote:

"If they [purported placebo effects] are known and can be controlled for, why are they still placebo? That doesn't make sense."

It makes total sense because placebo effects are exactly what a placebo controls.

I could go on, but I'll leave it to you to explain why any of the above statements would be correct in the context of a mouse study.


ETA: I've read the paper: https://www.internationalskeptics.com/forums/showthread.php?postid=14395913#post14395913
 
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When you're trying to find out whether a medical treatment actually works you need to carefully eliminate every confounding factor which might lead you to think it's having an effect when it actually isn't, whether those factors are real (i.e. measurable), all in the mind, or just the usual sources of error. Those who are interested only in whether the medicine they're testing is effective often lump all those factors under the umbrella term placebo effect. They don't care whether they're real, psychosomatic, errors, or a mixture of all three. They just want to eliminate them, and a double blind randomised clinical trial where the control group receive a placebo does that very well.

People who are interested in what those confounding factors are, and whether at least one of them might be real, often seem to reserve the term placebo effect for that subset of factors (a subset which might well be empty).

Having two definitions for the same term often causes confusion.
 
@arthwollipot: I have now read all of the mouse study paper except for the methods section. Nothing you wrote is correct in the context of that paper.
 
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When you're trying to find out whether a medical treatment actually works you need to carefully eliminate every confounding factor which might lead you to think it's having an effect when it actually isn't, whether those factors are real (i.e. measurable), all in the mind, or just the usual sources of error. Those who are interested only in whether the medicine they're testing is effective often lump all those factors under the umbrella term placebo effect. They don't care whether they're real, psychosomatic, errors, or a mixture of all three. They just want to eliminate them, and a double blind randomised clinical trial where the control group receive a placebo does that very well.
Yep.

People who are interested in what those confounding factors are, and whether at least one of them might be real, often seem to reserve the term placebo effect for that subset of factors (a subset which might well be empty).

Agreed, though Arthwolipot seems to have reserved the term for the opposite group of factors, not the subset that is real, but the subset that is not.
 
Very interesting, this latter part of the discussion.

artwollipot, I'm having trouble wrapping my head around your linguistic argument. You seem to be defining placebo as necessarily a sham; and cutting away those portions of it that turn out not to be a sham after all, as therefore definitionally not placebo.

I mean, if placebo by definition is a sham, then we don't need studies about that focused question. That question, 'Is placebo real or a sham'', would then be conclusively settled at the definition stage itself.

But on the other hand: take the term, 'paranormal'. We do define it as not existing. If we study its claims, and find some of its alleged manifestations to be valid, including even such crazy stuff like telepathy; then we do immediately shift that portion away from the head Paranormal and under the head Stuff-your-brain-has-evolved-to-do.

So in that sense such linguistic contortions need not necessarily be misplaced.

The linguistics is probably the least important part of all this; and clearly there's no unanimity on this; but just to be clear: Is that how you'd explicitly like to define 'placebo'? As something that, like 'paranormal', necessarily is something that definitionally does not and cannot exist?

----------

If what this report seems to be showing is true --- IF --- then does that mean that things like homeopathy etc might have some valid application after all, in the form of placebo (or whatever we call it)? Particularly in situations where bona fide treatment may not be available --- either because there is none at all, or because that specific person or populace doesn't have access to it?

(Not arguing that that's so. I'm asking if that might be so, after all, basis this somewhat different angle now introduced.)
 
@arthwollipot: I have now read all of the mouse study paper except for the methods section. Nothing you wrote is correct in the context of that paper.


What is your definition of placebo, then? I don't think you've spelled that out.
 
When you're trying to find out whether a medical treatment actually works you need to carefully eliminate every confounding factor which might lead you to think it's having an effect when it actually isn't, whether those factors are real (i.e. measurable), all in the mind, or just the usual sources of error. Those who are interested only in whether the medicine they're testing is effective often lump all those factors under the umbrella term placebo effect. They don't care whether they're real, psychosomatic, errors, or a mixture of all three. They just want to eliminate them, and a double blind randomised clinical trial where the control group receive a placebo does that very well.

People who are interested in what those confounding factors are, and whether at least one of them might be real, often seem to reserve the term placebo effect for that subset of factors (a subset which might well be empty).

Having two definitions for the same term often causes confusion.


I haven't actually looked this up or anything, but basis usage I've seen --- everyday usage, people-at-large usage --- there does seem to be more than one definition, then.

That mouse study --- I haven't checked it out, but basis what you all are saying about it --- seems to indicate that the expectation of the creature that something (good) might happen is what has triggered something (good) to happen. That corresponds with what many understand placebo to be, even if incorrectly.

Your definition is very clear. I'm sure it's right, not doubting that. But
(a) That latter thing, regardless of whether it actually happens, does it have a technically correct name, then?
(b) Is it real? The mouse study would seem to indicate it is.
(c) Assuming it is real, can otherwise ineffective "treatment" be administered in order to deliberately trigger that response?
 
artwollipot, I'm having trouble wrapping my head around your linguistic argument. You seem to be defining placebo as necessarily a sham; and cutting away those portions of it that turn out not to be a sham after all, as therefore definitionally not placebo.
Not quite. I'm defining the so-called "powerful placebo" aka "mind over matter" effect as promoted by acupuncturist Ted Kapchuk and others as a sham. Placebo effects are real - they are variables that are not controlled for in your study. Once you control for a placebo effect, it no longer plays a role in your study and you can look at what you're actually intending to look at.

That's why in studies of... say, ooh, acupuncture, the more tightly controlled your variables are, the smaller the effect size is. If you could reach the hypothetical "spherical cow" stage where all variables are controlled (which, like a spherical cow, is impossible), you would see that there is no effect at all.
 
(a) That latter thing, regardless of whether it actually happens, does it have a technically correct name, then?
The only term I've ever encountered is the placebo effect, with its inherent implication that it's not real.

(b) Is it real? The mouse study would seem to indicate it is.
It does, but it's just one study.

(c) Assuming it is real, can otherwise ineffective "treatment" be administered in order to deliberately trigger that response?
I suspect lots of doctors already use placebos to "treat" patients with symptoms they believe are psychosomatic. I guess this would be additional justification for doing so.
 
The only term I've ever encountered is the placebo effect, with its inherent implication that it's not real.


Not real isn't implied. What's usually implied is that it's psychological rather than physiological. The new study indicates that it's not just psychological but also neurological.

It does, but it's just one study.


Nobody claimed that the study was more than one study?

I suspect lots of doctors already use placebos to "treat" patients with symptoms they believe are psychosomatic. I guess this would be additional justification for doing so.


They may use placebos to treat psychosomatic symptoms, but they also prescribe or recommend them to treat symptoms that aren't psychosomatic: 'phlegm-dissolving' (a direct translation from Danish) cough medicine.
I don't know if any of the so-called expectorants have actual physiological effects on phlegm or mucus. Most of them don't - or a least they didn't 20 years ago.
 
Placebo effects ... are variables that are not controlled for in your study.

Again, no they are not. Placebo effects are precisely those variables that are controlled by using a placebo in the control arm of a study.

Once you control for a placebo effect, it no longer plays a role in your study and you can look at what you're actually intending to look at.

Reread that sentence above. It is correct because it implies your first sentence is wrong. Your first sentence says a placebo effect is an uncontrolled effect. Your second sentence says it is an effect you can control. In fact, placebo effects can be controlled or uncontrolled. In principle, a properly designed placebo-controlled trial controls for all placebo effects.

That's why in studies of... say, ooh, acupuncture, the more tightly controlled your variables are, the smaller the effect size is. If you could reach the hypothetical "spherical cow" stage where all variables are controlled (which, like a spherical cow, is impossible), you would see that there is no effect at all.

In your acupuncture example, if you controlled for all placebo effects, and the treatment effect disappeared, it would imply that the observed effect of acupuncture is entirely a placebo effect (again, illustrating that a placebo effect can be controlled).

But what makes you think it is necessarily impossible to control for all placebo effects? It might be difficult in an acupuncture study, where it is probably impossible to blind the acupuncturist, but designing good placebo-controlled trials for other treatments are more straightforward. If your experimental treatment is a pill comprising an active ingredient embedded in an inert medium and your placebo is that exact same pill minus the active ingredient, why would that not completely control for any possible placebo effect of the active treatment?
 
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What is your definition of placebo, then? I don't think you've spelled that out.


Take a look at this post of mine. It doesn't give a formal definition, but perhaps explains the concept even better than a formal definition would. If you still have questions, I can then address them.
 
When you're trying to find out whether a medical treatment actually works you need to carefully eliminate every confounding factor which might lead you to think it's having an effect when it actually isn't, whether those factors are real (i.e. measurable), all in the mind, or just the usual sources of error. Those who are interested only in whether the medicine they're testing is effective often lump all those factors under the umbrella term placebo effect. They don't care whether they're real, psychosomatic, errors, or a mixture of all three. They just want to eliminate them, and a double blind randomised clinical trial where the control group receive a placebo does that very well.


I think you are defining "placebo effect" too broadly. Placebo effects are precisely those effects that a placebo can control. But there are lots of biases that need to be controlled that have nothing to do with whether a placebo is used or not, for example, regression to the mean, Hawthorne effect, imbalance in prognostic factors, period effects, differential compliance, etc.
 
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It does, but it's just one study.
I don't believe it does. It establishes one pathway for endorphin release in the absence of stimulus by classical conditioning. It could be that this pathway for pain relief contributes to a placebo effect, but it also might not be involved at all.

The existence of this pathway alone does not demonstrate that the so-called "Powerful Placebo" effect is real.
 
arthwollipot, Pixel42, jt512,

Thanks for your recent responses. That does clarify it for me.

As I see it now, “placebo” is the thing you administer during the trial or the study, like the glucose pill or whatever; “placebo effect” refers to the effects specifically of this placebo thingie; and the thing I referred to, what the great unwashed wrongly believes is the placebo effect (and as I used to also, prior to reading this thread, even though I do shower or bath every day, oftentimes twice) is correctly referred to as the “powerful placebo effect” or the “strong placebo effect”.

I appreciate you guys have minor disagreements over the details of those definitions, but by and large that’s about it, I think.

And it seems that, basis this study, the powerful placebo effect is apparently a thing. As has been rightly pointed out, though, it’s just one study, so there’s some way to go before we actually proclaim it a thing. And I suppose if does turn out to be a thing, then we’ll christen it something-or-other, that particular mechanism of what seems to have happened there; and then I suppose we’ll stop calling it “powerful placebo”, even thought people at large might continue to do that.

Do please correct me if I’ve got any of that wrong.

Also, I see that there’s one dissenting voice, that says this study does not demonstrate the powerful placebo effect. I’ll address that separately --- for what that’s worth, my addressing it I mean, it’s you guys who know all about this who’ll have to settle the question amongst yourselves, I’m just along for the ride, from the back seat as it were.
 
The only term I've ever encountered is the placebo effect, with its inherent implication that it's not real.


It does, but it's just one study.


I suspect lots of doctors already use placebos to "treat" patients with symptoms they believe are psychosomatic. I guess this would be additional justification for doing so.


As far as the highlighted: Not quite what I was going for. Sure, doctors in practice do all kinds of things, that may or may not be valid or warranted. But if what this mouse study shows does turn out to be a thing --- it doesn’t yet, as you say it’s just one study, but if other studies do end up bearing it out --- then in certain circumstances such prescriptions may be turn out to be perfectly valid, isn’t it. And also, as dann points out, not just for psychosomatic symptoms, right?
 
I don't believe it does. It establishes one pathway for endorphin release in the absence of stimulus by classical conditioning. It could be that this pathway for pain relief contributes to a placebo effect, but it also might not be involved at all.

The existence of this pathway alone does not demonstrate that the so-called "Powerful Placebo" effect is real.


Not sure why you think that. That is, absolutely, it’s just one study, like Pixel42 says, and one single study cannot be thought of as conclusive evidence, not even close; but so far as that study goes, it does to seem to demonstrate your powerful placebo thingie, doesn’t it.

I’m sorry, I haven’t looked up the report proper --- and the details of what I’d read through, way back when you’d first started the thread, are kind of dim in my memory by now! --- but basis what I’ve seen others say here in recent posts, you drag the mouse across to a spot where typically it’s administered some kind of relief, and, once the mouse gets accustomed to “expecting” that relief, then that relief seems to be forthcoming even when it’s administered nothing at all. That would seem to be exactly what the powerful placebo effect is, isn’t it.

I suppose the equivalent in us humans would be to take you --- or me --- across to Lourdes, or Mecca, or Benares, and our persistent backache, or persistent migraine, disappears just like that. Because we’d expected it to. Something like that. Or we’re administered homeopathic pills, or, as you say, acupuncture, and boom, we’re better. Something like that.

Again, I realize this one study isn’t close to being definitive. But so far as it goes, what it indicates seems clear. That we might identify the specific neural route via which that relief mechanism occurs means only that we identify that route, that doesn’t negate the effect itself, surely.
 
Not sure why you think that. That is, absolutely, it’s just one study, like Pixel42 says, and one single study cannot be thought of as conclusive evidence, not even close; but so far as that study goes, it does to seem to demonstrate your powerful placebo thingie, doesn’t it.

I’m sorry, I haven’t looked up the report proper --- and the details of what I’d read through, way back when you’d first started the thread, are kind of dim in my memory by now! --- but basis what I’ve seen others say here in recent posts, you drag the mouse across to a spot where typically it’s administered some kind of relief, and, once the mouse gets accustomed to “expecting” that relief, then that relief seems to be forthcoming even when it’s administered nothing at all. That would seem to be exactly what the powerful placebo effect is, isn’t it.

I suppose the equivalent in us humans would be to take you --- or me --- across to Lourdes, or Mecca, or Benares, and our persistent backache, or persistent migraine, disappears just like that. Because we’d expected it to. Something like that. Or we’re administered homeopathic pills, or, as you say, acupuncture, and boom, we’re better. Something like that.

Again, I realize this one study isn’t close to being definitive. But so far as it goes, what it indicates seems clear. That we might identify the specific neural route via which that relief mechanism occurs means only that we identify that route, that doesn’t negate the effect itself, surely.
Again, we're getting hung up on something that was not the point of Mike Hall's article.

It doesn't matter. The study did not do what the media claimed it did - which was to explain and control "the placebo effect". It demonstrated one biochemical mechanism that might contribute to a placebo effect, or might not. The media is blowing it all out of proportion, as usual.
 
Again, we're getting hung up on something that was not the point of Mike Hall's article.

It doesn't matter. The study did not do what the media claimed it did - which was to explain and control "the placebo effect". It demonstrated one biochemical mechanism that might contribute to a placebo effect, or might not. The media is blowing it all out of proportion, as usual.


I haven't read Mike Hall's article. Or if I had, back around the start of this thread, then I've forgotten by now. And the fact that media tend to sensationalize, that's nothing new. ...To me at least, the important point is, does this study demonstrate the placebo effect (in the technically incorrect sense, in the sense that people understand it commonly)? And that is the part I'd like to have cleared up.

Others are saying it does. You're saying it doesn't. Now I don't presume to be anything close to anything remotely resembling an expert, but as best as I can make out, on this they're right and you're wrong. I mean, take the highlighted:

Take the second sentence first. How might it NOT, as you say, "demonstrate one biochemical mechanism that might contribute to a placebo effect"? How? Of course, this is just one study, and therefore not definitive; but so far as it goes, demonstrate one biochemical mechanism that might contribute to a placebo effect is exactly what it seems to have done. As far as I can make out, basis my admittedly sketchy idea of what's going on. (Happy to correct that impression of mine if you can clearly explain why that's not so, and how that "might not" of yours might kick in.)

If we remove the "or might not", then the second sentence in the portion I've highlighted seems right to me. And basis that second sentence (minus the "or might not"), your first sentence does not follow; in fact in that case the second sentence is saying exactly the opposite of what that first sentence says. (As far as I can make out. Again, happy to correct my impression if you can clearly explain why that's not so.)
 
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If we remove the "or might not", then the second sentence in the portion I've highlighted seems right to me. And basis that second sentence (minus the "or might not"), your first sentence does not follow; in fact in that case the second sentence is saying exactly the opposite of what that first sentence says. (As far as I can make out. Again, happy to correct my impression if you can clearly explain why that's not so.)

I think I get and actually agree with that part of Arth's view: there are many different effects being controlled for with placebo, and this study only shows one such effect. In many cases where placebo controls are necessary, this effect probably isn't involved at all. For instance, early in the thread there was discussion of a surgery that was studied with placebo control (they basically did the exploratory part without the intervention part of the surgery, so the patient was still put under anesthesia and still had to be cut open). The result of that study was that the placebo group and the intervention group had similar results, suggesting that the actual intervention was ineffective.
I think there's a third control group with no intervention, including placebo, (though I may remember wrong), who did worse than both. But I doubt that the reason the placebo group does better than that control is because of an actual physiological mechanism. In that case, it's probably just all the issues of subjective reporting that have been discussed in this thread.

So, to sum up, there may actually be cases where there's a real physiological mechanism involved in placebo effects. The mouse study is evidence in that direction. But there are also other effects involved, and its very likely that in many (most?) cases there is no physiological mechanism involved. Saying "this study explains the placebo effect" suggests that this is the whole of what the placebo effect is, whereas it is at most a contributing factor in some cases.
 
But if all those other effects are confounding factors - doctors and patients who don't want to disappoint each other and/or who hope that something positive has been achieved in the patients' symptoms, or regression to the mean, which would have been achieved with or without the alleged placebo but is nevertheless contributed to the pill, etc. - then they aren't something that should be considered to be part of any actual, i.e. not psychological, placebo effect in as far as they may affect reporting but don't contribute to relieving any pain, cough or phlegm.

They may nevertheless still serve the purpose that placebos serve in double-blinded RCTs because neither the two groups nor their doctors can tell the difference between the two kinds of pills/treatments, i.e. psychologically there's no difference between the two groups and reporting errors are thus eliminated because the reporting about the placebo pills and the actual drugs get the same 'placebo benefit'.
 
Yeah, I seem to recall a This American Life years ago reporting on people with debilitating digestive issues that wouldn't clear up no matter what, until one day they'd get a doctor with basically really good bedside manners and suddenly the treatments would work and they'd get better. It's been forever since I heard it but the impression I got was that feeling hopeless/like the doctor didn't really care, was a powerful NOcebo effect for these people.

If this is an effect we can consistently create/avoid then it's worth doing. Studies have yet to show if it's essentially an anecdotal effect or a replicable one, besides this mouse study showing (one) measurable physiological effect of expectation.

But IMO whether there is a strong health outcome difference or not, to feeling like your doctor cares AND is doing something that may help, vs feeling like your doctor thinks you're a kook and is only doing something that would help with whatever the doctor thinks is wrong with you... I'd be happy just being less pissed off and more gratified by my health care providers. It's not like a doctor has to go, kind, competent, pick one.
 
I think I get and actually agree with that part of Arth's view: there are many different effects being controlled for with placebo, and this study only shows one such effect. In many cases where placebo controls are necessary, this effect probably isn't involved at all. For instance, early in the thread there was discussion of a surgery that was studied with placebo control (they basically did the exploratory part without the intervention part of the surgery, so the patient was still put under anesthesia and still had to be cut open). The result of that study was that the placebo group and the intervention group had similar results, suggesting that the actual intervention was ineffective.
I think there's a third control group with no intervention, including placebo, (though I may remember wrong), who did worse than both. But I doubt that the reason the placebo group does better than that control is because of an actual physiological mechanism. In that case, it's probably just all the issues of subjective reporting that have been discussed in this thread.

So, to sum up, there may actually be cases where there's a real physiological mechanism involved in placebo effects. The mouse study is evidence in that direction. But there are also other effects involved, and its very likely that in many (most?) cases there is no physiological mechanism involved. Saying "this study explains the placebo effect" suggests that this is the whole of what the placebo effect is, whereas it is at most a contributing factor in some cases.


If that’s what arthwollipot meant, then certainly I agree with him, and with you. But that's a somewhat odd way of putting it, then. …I mean, take the paranormal, that I referred to earlier:

Let’s say, hypothetically, that, crazy as it sounds, one of those nutjobs that used to come up on the earlier JREF threads, claiming they could read your mind, and divine the numbers you’ve thought of continents away from them, is indeed able to convincingly support this claim of theirs of the paranormal. Or maybe they do that in a full-on lab study, not just here, online. Point is, let's assume they do it. ...Well now, first of all, that only demonstrates that some kinds of telepathy sometimes work, not that every kind of telepathy therefore works; and it most certainly does not indicate that every claim of telepathy is therefore true. Second of all, it is a demonstration only of telepathy, and not of other kinds of paranormal claims like, I don’t know, dowsing, and prophesying future events, and speaking with the dead, and recollection of “past life” memories from long ago. But despite that, it wouldn’t really make sense to therefore assert that reports that this experiment demonstrates the paranormal are wrong. It does indeed prove the paranormal, and it would certainly merit the million dollars, had that still been on offer. Right?

…In any case, let’s not get hung up over whether that precise wording works or not, or whether some podcaster meant something correctly, or whether some news report’s been sensationalized. Like I said, to me the really important thing, that I wanted to be clear about, is that this experiment does seem, so very unexpectedly, to indicate that expectations can drive physiological relief for causes that are not themselves psychosomatic in nature. …What Pixel42 said earlier, that this just one study, and therefore not definitive, makes sense, absolutely; and we should wait before more studies prove this more conclusively, and not rush to believing just yet that this very extravagant principle is a thing. …That said, if indeed this is true, then surely that’s a …huge, really huge thing? Because that might end up opening up valid application of this principle across categories that we’d thought have been completely debunked and rejected, like healing by touch, and healing by pilgrimage, reiki, chakric healing, acupuncture, homeopathy, the works --- in very limited cases, for instance when bona fide treatment is not available or is medically inappropriate, and that too for very specific kinds of ailments not everything under the sun, but still.
 
But what makes you think it is necessarily impossible to control for all placebo effects? It might be difficult in an acupuncture study, where it is probably impossible to blind the acupuncturist, but designing good placebo-controlled trials for other treatments are more straightforward. If your experimental treatment is a pill comprising an active ingredient embedded in an inert medium and your placebo is that exact same pill minus the active ingredient, why would that not completely control for any possible placebo effect of the active treatment?

I suspect this is due to a misunderstanding over what 'control for' means.
 
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