The Placebo Effect In 60 Seconds

January 1, 2011 at 3:53 pm (Placebo) (, , , , , , , , , , , )

In which I attempt to explain a phenomenon I do not understand. Within an arbitrary time limit.

What is it?

The placebo effect relies on belief, expectation. Sometimes, “placebo effect” is used as shorthand for “any improvement not attributable to an active intervention” – this improvement could be due to a number of factors. When used in this way, the term does cover the true placebo effect, but it also includes the following:

Spontaneous improvement, fluctuation of symptoms, regression to the mean, additional treatment, conditional switching of placebo treatment, scaling bias, irrelevant response variables, answers of politeness, experimental subordination, conditioned answers, neurotic or psychotic misjudgment, psychosomatic phenomena, misquotation, etc. [Kienle and Kiene, 1997]

The true placebo effect is what Moerman and Jonas referred to as the meaning response.

Ernst and Resch tried to differentiate between the perceived and the true placebo effect in a 1995 paper in the BMJ.

How important is it?

HK Beecher wrote an influential paper in 1955 titled “The powerful placebo”. A 1997 paper by Kienle and Kiene asked whether Beecher’s powerful placebo was fact or fiction. [PDF here.] They claimed that “awareness of Beecher’s mistakes and misinterpretations is essential for an appropriate interpretation of current placebo literature”.

Fight, fight…

Scientists love arguing about ideas, and the placebo effect is a good arena for these intellectual gladiators.

Hróbjartsson and Gøtzsche asked Is the Placebo Powerless? in a paper published in NEJM and found little evidence in general that placebos had powerful clinical effects.

Disagreement came from (among others) Wampold et al – responded to by Hróbjartsson and Gøtzsche here. Hunsley and Westmacott offer this, in which they note that “Meta-analytic results reported by the two sets of authors are nearly identical”.

Hunsley and Westmacott go on to argue that placebo effects do exist and cannot be dismissed as unimportant – but also that it is reasonable to describe the effect size for placebos in medicine as small.

My conclusions

The placebo effect is real, is often misunderstood, and there is some controversy as to just how powerful it is.

It’s also pretty damn interesting.


A couple of interesting links:

Neurobiological Mechanisms of the Placebo Effect

Lee Crandall Park MD on placebo where inert nature disclosed: link, PDF; a newer paper on placebo for IBS without deception: PDF.

The bias of compliance: “…people who take their placebo regularly are just different than the others. The rest is a little speculative. Maybe they take better care of themselves in general. But this compliance effect is quite a big effect.”

Edit, 2nd October 2011: At least in this study, it appears that a placebo effect can operate when the outcome of interest is self-rated improvement, but not when an objective outcome is used. This finding is in accordance with what Hróbjartsson and Gøtzsche originally reported…



  1. disgruntledphd said,

    You might also want to look at the Meissner et al 2009 study on placebo, which qualifies the other meta-analyses in some interesting ways.

    Meissner Distal et al 2009 placebo effects on physical but not biochemical outcome parameters. Sorry, i’m too lazy to get the link now, but Google scholar should point to the right paper.

  2. Oliver Dowding said,

    And all those dear boring animals that cannot spell or understand the meaning of placebo…….how inconvenient of them to run such theories of placebo “out of town”, in most cases. Which often include mass treatments of groups or flocks etc.

    Nothing intellectual about them, just mundane biological beings responding positively time and again – and no, not because their keepers “think” they got better, nor because said keepers “suggested” to them that they would get better. Unless there is some serious credit to be given to psychic powers of herdsmen et al.

  3. jdc325 said,

    Hello again Mr Dowding. I thought we’d covered your objections to the suggestion that the placebo effect is relevant to treatment of animals in this earlier thread: link. We also ran through your arguments again on this thread. At one point in the latter thread, I pointed out that

    There is a critique of Beecher’s paper on placebo that includes the following: “False impressions of placebo effects can be produced in various ways. Spontaneous improvement, fluctuation of symptoms, regression to the mean, additional treatment, conditional switching of placebo treatment, scaling bias, irrelevant response variables, answers of politeness, experimental subordination, conditioned answers, neurotic or psychotic misjudgment, psychosomatic phenomena, misquotation, etc.” The observation of improvements seen in animals or humans can be partly due to a combination of the above-listed factors as well as the placebo effect and the effect of a treatment given.

    You didn’t seem to have an answer to this.

    Later on in the same thread, I said

    There are several possible reasons for the perceived improvements in animals treated with homeopathy, all of which are more likely reasons for the perceived improvement than homeopathy. I have listed these reasons more than once, and have drawn your attention to them to ensure that they have not escaped your notice. You seem intent on ignoring them.

    Your response was this:

    I’m definitely not ignoring these comments, it’s just that they’re so laughable as to be worth no comment.

    Are you really telling me that you are happy to believe in the power of magic water and sugar pills, but find it impossible to believe that any of the factors I mentioned (spontaneous improvement, fluctuation of symptoms, regression to the mean, additional treatment, conditional switching of placebo treatment, scaling bias, irrelevant response variables, answers of politeness, experimental subordination, conditioned answers, neurotic or psychotic misjudgment, psychosomatic phenomena, misquotation, etc.) could be responsible for any perceived improvement in the health of animals?

    The bottom line is that homeopathy cannot work, it does not work, and you are simply in denial of the facts.

  4. Oliver Dowding said,

    Please yourself, if that’s what you want to believe. I’m not in denial of anything other than your interpretation of homoeopathy. Of course, I don’t believe in the power of water to be called magical, all that sugar pills can resolve anything. But then, don’t think that I’m gullible enough to believe that homoeopathy is administering just sugar pills, or water mixed with alcohol. It’s not. I don’t ask you to believe that.
    I don’t dismiss that on some occasions, people may recover spontaneously. But to think that all the successful results from homoeopathy are entirely due to the fact is you mention, is plainly wrong.

    You’re absolutely right, I don’t understand the science of how it works, but frankly it ha been said many times in many posts that all these requests are pretty irrelevant. The practical evidence is there to be seen.

    There are plenty of people, fortunately, prepared to accept that something works and has an effect, but which they may not understand the mechanism of efficacy, , but following the administration of such remedy the results and benefit to the patient are clearly apparent to all to see. And no, it’s not cognitive bias!

    It does not need an RCT type trial to prove whether homoeopathy works or doesn’t. Again, has been said many times, why don’t you come down onto a farm, talk to a qualified vet, who is also dual qualified in homoeopathy, and discuss the efficacy or not?

    I’ve offered this option on many occasions before, not just on these forums, but others, and strangely every sceptic or critic of homoeopathy has failed to respond positively. Whatever could be causing this dismissal of the offer? You could talk to the homoeopathic supplier, who I know, treating a chicken flock of 180,000 birds. There’s no way you’re going to conduct an RCT on that lot. Equally, a farmer friend
    assures me of the significant results he’s achieved with homoeopathy on his free range chicken flocks, where all the conventional remedies he’d been allowed to use (under organic regulations) had failed to make any improvement in the ailments of the hens. The homoeopathic remedy resolved the problem almost immediately, and with constant monitoring and revision of the remedy needed at any one time, the chicken’s health has been kept in excellent balance since.

    So, how about your coming down to see a veterinary surgeon, an MRCVS, and discuss the cases that they deal with on a regular basis, professional to professional? I think you would then understand that it isn’t relevant to try and conduct homoeopathic trials under RCT type guidelines.

    I think you would also understand that much as you may think some sort of power of suggestion is the reason for success in treating animals with homoeopathy, and your co-belief that the animal would have recovered regardless of what treatment was administered, etc, this is misplaced. In re-reading a couple of last years blogs, and the many posts placed within them, I can’t help noticing how you strenuously, and those of the same opinion as yourself, avoided being drawn in to having to individually go down and meet with the homoeopathic vet or a farm using
    homoeopathy successfully et al, and see what they’re doing on the ground. I think until you are prepared to do that, you will continue to misunderstand both what homoeopathy is – most definitely not sugar and water, a surprising comment for a scientist to make. There must be some element of something within it, that is causing the millions of animals to recover. It’s simply not possible to dismiss millions and millions of treatments as being human misunderstanding. Once again, I suggest that you could recommend to all the conventional world that they start using this sugar and water, because it is so wonderfully cheap, and apparently delivers efficacy even though you don’t understand why.

    Finally, just to remind you, I’m not a scientist, I don’t have endless hours at my disposal, I don’t have a laboratory or staff to write up scientific experimentation results, I don’t have the resources of endless scientific journals to reference, etc. All I do have, which I appreciate it’s very difficult for you to cope with, is many years of practical experience and observation Plus, I have an open mind – if not I would never have had the nerve to trial homoeopathy, nor to risk the health and well-being of my animals, nor to ask herdsmen to use the medication.

    Oh, sorry, I forgot that you don’t think its observation. We are being deluded by animals into thinking they got better, even though there were far too many of them (thousands in my case, 100’s of milliions globally) for me and others to be watching all of them closely, and to be deluded by. I’ll leave you to carry on, thinking the way you do, and await your uptake of the invitation offered. When you have responded positively to that, I will then attempt to locate somebody with whom you can meet, and the farm on which you can meet them.

    Happy New Year

  5. jdc325 said,

    why don’t you come down onto a farm, talk to a qualified vet, who is also dual qualified in homoeopathy, and discuss the efficacy or not?

    You could talk to the homoeopathic supplier, who I know, treating a chicken flock of 180,000 birds.

    Tell you what, as a starting point why don’t you pass my email address to the vet and homoeopathic supplier? I’d be more than happy to discuss homoeopathy with either or both of them. It’s 325jdc325 (at)

    Happy New Year.

  6. Cybertiger said,

    jdc523 twittered,

    “The placebo effect is real, is often misunderstood … ”

    Of course, jdc235 doesn’t understand the placebo effect any more than he does anything else. But Dr John Briffa has recently written some interesting thoughts on the placebo effect …

  7. JustJobe said,

    All i get from people like Dowding is:

    “Hey, it’s OK to make money selling something untested to the masses. Just say you are not trained to understand it, and therefore no one can question you about it. If anyone does ask, go ahead and tell them to figure it out for themselves.”

    Best product for a salesman ever!

    Can you imagine if real medical professionals started selling untested meds out there like that? There’d be a lynching…

  8. Michael Ringland said,

    And a happy new year to you all as well….My two bobs worth is a study I heard of about chiropractic treating childhood asthma found the best result (apart from the boring standard medical treatment) was when the practitioner had lots of certificates on the wall, wore a white coat, and pretended to give a shit. My experience (as a physiotherapist) is that quite a few doctors/nurses DON’T give a (lets say) Damm about their professional responsibility. I have seen doctors selling “untested meds” for profit lots of times. Glucosamine for knee pain would be one example. So, dear friends, don’t paint the medical profession as all “white” and the homeopathic mob as all “black”. There are shades of grey. I never treated a condition without having a firm BELIEF that it would help (maybe not cure, but help). That made me a prime candidate for allowing as much placebo as I could muster on my patients behalf. The thing that changes my belief that a treatment works as against KNOWING its working is: I measured (in degrees) an improved range of movement, or measured (using VAS pain scale) to monitor pain in the most valid way I knew. That way the well known “Hawthorn effect” – that is the patient will tell you how much better they are, even if they are not better at all, because we are well meaning practitioners, who try really hard. If I believed everything patients told me my ego would be bigger than it already is!! I tried a few months talking to WDDTY people, but gave up. Their belief in homeopathy and light energy is tiresome, but thats their right, and if you really believe that flavoured water can do much apart from relieve dehydration, we can never agree on matters medical. MOVE ON, OK? peace be with you my brothers and sisters (from an old hippy)

  9. jdc325 said,

    Sadly, I’ve not yet heard from Oliver Dowding, the vet, or the homoeopathic supplier.

  10. You Couldn’t Make It Up: Paper Remedies « Stuff And Nonsense said,

    […] Remarkable? I don’t think so. Someone fully expects something to work and they then perceive an effect. The thought that the perception may be false apparently does not cross the mind of the OP. The idea that expectation can affect perception of severity of symptoms seems to be alien to this poster. It’s almost as if they’ve never heard of the placebo effect. […]

  11. Homeopathic Anecdote On The One Show « Stuff And Nonsense said,

    […] cleared up following use of a homeopathic product. I wonder how much Alex Jones knows about the placebo effect. I’d also be interested to learn whether she is aware of the following: Spontaneous […]

  12. An A-Z of Alternative Medicine « Stuff And Nonsense said,

    […] alternative treatment will include placebo effects. The benefits will, in most cases, be limited to placebo. Treatments that can be shown to have significant effects beyond placebo cease to be alternative […]

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