Evolution could explain the placebo effect | Hacker News Reader

Evolution could explain the placebo effect

newscientist.com

43 pointsmmahemoff28 comments

"Evolution could explain the placebo effect"

Umm... what else could explain the placebo effect?

Evolution can explain every biological aspect ever to have existed if you take it to a broad enough level

It is healthy to be wary of "evolution explains X" claims. As you say, evolution theory is intended to explain all biological developments. That doesn't mean that any particular evolutionary pressure we can conceive of that logically leads to the effect is the real explanation.

Yes, but the headline is still funny. "Evolution could explain the placebo effect" is a fantastic understatement - evolution almost certainly explains the placebo effect. "We could have found the evolutionary explanation for the placebo effect" is less snappy, though, I guess.

Methinks you need to refine your definition of 'explain'.

Not really. Evolution only explains the persistence of traits which influence survival and reproduction. It can't explain why those traits arose in the first place (random mutation), or the existence of traits which don't affect survival or reproduction. It also can't explain why some traits never arose at all (say, winged humans).

And to be really nitpicky, "evolution" is the observed fact that species change over time. It isn't an explanation at all. Natural selection is the explanation for evolution, both in general, and for specific traits.

Random mutation and natural selection. One's a generator, the other a filter.

In the same sense that Physics can explain it...

It might be better to refer directly to psychology and neuroscience to explain the placebo effect

From the Nicholas Humphrey paper cited in the post:

"My view is this. The human capacity for responding to placebos is in fact not necessarily adaptive in its own right (indeed it can sometimes even be maladaptive). Instead, this capacity is an emergent property of something else that is genuinely adaptive: namely, a specially designed procedure for 'economic resource management' that is, I believe, one of the key features of the 'natural health-care service' which has evolved in ourselves and other animals to help us deal throughout our lives with repeated bouts of sickness, injury, and other threats to our well-being".

in full here: http://www.humphrey.org.uk/papers/2002GreatExpectations.pdf

FTA: We subconsciously respond to treatment - even a sham one - because it comes with assurances that it will weaken the infection, allowing our immune response to succeed rapidly without straining the body's resources.

I wonder if there isn't an alternative explanation, that the placebo effect may be an elaboration of the human social instinct. Consider how a control patient in a drug trial must feel when they are not given any treatment. Perhaps receiving the pill is an act of symbolic inclusion in the tribe that cues the immune system that the individual has a better outlook because they will be cared for by others.

> I wonder if there isn't an alternative explanation, that the placebo effect may be an elaboration of the human social instinct.

You read my mind. We're social animals. Hamsters may respond to sunlight, human beings respond to communal support. We have plentiful food stores when we are supported by our community and have none when we are abandoned. We're not hamsters.

Somebody bothering to place you in a study, ask you dozens of questions, then give you medicine ... at no cost to you ... doesn't that scream social support?

I wonder if a placebo would be just as effective if taken at home as a Tylenol or similar.

"I'm pleased to see that my theory stands up to computational modelling,"

Was anyone else disturbed by that statement?

We all know that models are heavily dependent on parameters, and by tweaking them you can get whatever result you want. The only use a model has is when it shows a pattern of predicting observations in the real world. In other words, a model is essentially a theory about the way the world works.

So "stands up to computational modeling" strikes me as a very unscientific thing to say -- kind of like saying "my theory stands up to his theory". Theories should stand up against testing and observations in the real world.

Without reading the context, I expect that 'computational modeling' refers to a largely mathematical model that is potentially agnostic about underlying causes. You can run simulations that accurately reflect the real world using one set of variables, then run another model (or somehow test another model) that confirms the original simulation's results from a different perspective; ie, you have two theories, and you validate the second by proving its equivalent to the first, even though it uses a different set of variables, or looks at it using a different theoretical framework.

of course, you're right that this can be troublesome. just because you can validate a theory as accurately modeling reality doesn't mean that the components of the model are true or useful.

and necessarily, the first 'computational model' would have needed to be already validated before something else might be validated against it...in case that wasn't clear.

Because the submitted article mentions the placebo effect, in the usual manner of popular articles, perhaps I should share here some links that are helpful for understanding what placebo effects are all about. Some of these online links cite quite a few useful scholarly publications.

http://www.sciencebasedmedicine.org/index.php/michael-specte...

"In other words, the best research we have strongly suggests that placebo effects are illusions, not real physiological effects. The possible exception to this are the subjective symptoms of pain and nausea, where the placebo effects are highly variable and may be due to subjective reporting."

http://www.sciencebasedmedicine.org/index.php/angells-review...

http://theness.com/neurologicablog/index.php/the-rise-and-fa...

http://www.sciencebasedmedicine.org/index.php/placebo-effect...

http://www.skepdic.com/placebo.html

http://www.sciencebasedmedicine.org/index.php/revisiting-dan...

The statement in the article kindly submitted here, "Someone suffering from a low-level infection will recover just as nicely whether they take an active drug or a simple sugar pill" should be interpreted as "Animals have a lot of capacity for recovering from infections, and some treatments for infections are indistinguishable in outcomes from doing nothing" until a citation for a specific study involving infection in HUMAN subjects is brought into the discussion. Usually the "placebo effect" is just the no-op effect of the body healing over time with the body's own healing mechanisms, and the ONLY reliable findings of placebo effects in human medicine, according to the sources I am citing here, are self-reported subjective symptoms like pain and discomfort, not physiologically verifiable improvement in disease states.

So let's not rush too fast to assume an explanation for a phenomenon until the phenomenon is better defined. The submitted article goes on to discuss some animal studies related to seasonal patterns of light and darkness. These studies are related to the idea that the immune system is costly to maintain, drawing on many physiological resources of the living organism. That's a reasonably important point and is indeed the subject of much ongoing research. But human beings, with their very complicated behavior patterns for adaptation to many environments, probably have a system for regulating immune response that is harder to observe. I note for the record and for your reading enjoyment that the recent book he Folly of Fools: The Logic of Deceit and Self-Deception in Human Life by Robert Trivers

http://www.amazon.com/The-Folly-Fools-Deceit-Self-Deception/...

includes a chapter, with some citations to scientific studies, about immune system interaction with the brain suggesting a theory of self-deception in the aid of bodily healing, on evolutionary grounds. The whole book is interesting, and there is better established findings in it, so it is well worth a read whatever other science says about placebo effects.

The article from science based medicine is fantastic. To quote:

"Recently the main special pleading we have been hearing is that CAM modalities work through the placebo effect. That is why they are so desperate to represent the placebo effect as something more than it is"

I think this is a very important point. In years past, all my 'alternative' friends would throw out all kinds of wild statements on how their treatments would work, safe in knowledge that it had not been conclusively disproved. Now that the gray area they reside in is being shut down, I've noticed a lot more lately that conversations end with "well, I just do it for the placebo affect". I never really noticed how often I hear this until I read the article. And now that even that gray area is being shut down, it makes me wonder what special pleading is going to be next.

> But human beings, with their very complicated behavior > patterns for adaptation to many environments, probably have > a system for regulating immune response that is harder to > observe.

That, and even when playing along with this case, it would seem logical for our immune system to conserve these precious resources by relaxing and taking it easy when we know some medicine is going in to help us rather than go full throttle.

You might like Irving Kirsch's book The Emperor's New Drugs. It's all about the placebo effect as it relates to antidepressants, but also more generally. I know with depression specifically the difference between placebo treatment and no treatment is actually quite large.

Also, that skepdic link is severely flawed. There isn't one placebo effect, but rather a series of placebo effects. There isn't any reason to think that using a sugar pill to treat pain would have roughly the same efficacy as using gardening to treat heart disease, which is what the skepdic article basically claims.

That may be true, but in my personal experience I had to try a several different anti-depressants before I found one that worked.

That may have been the case, but research shows that it often takes several different placebos to find one that works. In fact, the chances of depression remitting when changing antidepressants are comparable to the chances of a disease being treated when changing placebos.

You are my favorite person of the day, because when I saw this post title, I said "Oh great, now I'm going to spend my morning writing another comment about how the placebo effect is probably mostly an illusion," and now I am released from that yoke.

"In other words, the best research we have strongly suggests that placebo effects are illusions, not real physiological effects"

not true!

see:

" Recent research demonstrates that placebo effects are genuine psychobiological phenomenon attributable to the overall therapeutic context, and that placebo effects can be robust in both laboratory and clinical settings. Evidence has also emerged that placebo effects can exist in clinical practice, even if no placebo is given. Further promotion and integration of laboratory and clinical research will allow advances in the ethical harnessing of placebo mechanisms that are inherent in routine clinical care and the potential use of treatments to primarily promote placebo effects."

from:

Placebo Effects: Biological, Clinical and Ethical Advances (Damien G Finniss, Ted J Kaptchuk, Franklin Miller, and Fabrizio Benedetti

PMCID: PMC2832199 / NIHMSID: NIHMS169379

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2832199/

"Conclusions:

It is evident that placebo effects are real and that they have therapeutic potential. Laboratory evidence supports the existence of numerous placebo mechanisms and effects in both healthy volunteers and patients with a variety of medical conditions. Furthermore, clinically relevant evidence demonstrates that placebo effects can have meaningful therapeutic effects, by virtue of magnitude and duration, in different patient populations. Although substantial progress has been made in understanding placebo effects, considerable scientific work remains to be done in both laboratory experiments and translational clinical trial research, with the ultimate aim of harnessing placebo effects to improve patient care. "

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2832199/

I had better respond to this reply, which I see is NOT responsive to the references I supplied in my original post. The link shown here, to a paper co-authored by Ted J Kaptchuk, was surely submitted here in good faith, and I thank the user who submitted it for that, but in fact Mr. Kaptchuk (he is NOT a doctor and does not have good training in human physiology or research methods) is well known as a promoter of ideas about healing through thinking that have no factual basis and are not backed up by science. Basically all roads to strong statements about "placebo effect" lead back to writings by Ted J Kaptchuk, which are heavily promoted by press releases.

So I invite all readers of Hacker News to compare the references I supply in this thread to the references supplied for the proposition that there are clinically meaningful placebo effects that actually heal disease in human patients. I especially encourage everyone reading this thread to review all the cited studies with the checklist by Peter Norvig, Google's director of research, "Warning Signs in Experimental Design and Interpretation"

http://norvig.com/experiment-design.html

in mind as you read the studies. Statistically valid, carefully designed research studies do NOT show clinically useful placebo effects. Preliminary studies by researchers who promote "alternative medicine" occasionally show patient self-reports of benefits in subjective symptoms (pain or discomfort) from placebo. Those have not been replicated by independent researchers.

Careful studies do not show healing of disease from administering placebos or by other mind-over-matter processes. Extraordinary claims require extraordinary evidence, and the burden of proof is on people (people without medical training and clinical experience, let me remind you) who claim that anyone can cure serious disease with a mere placebo effect.

The reply above prompted me to rewrite my original comment here (the comment that is "grandfather" to this comment) as a FAQ file. I'll post that below.

http://www.sciencebasedmedicine.org/index.php/michael-specte...

Despite the numerous press releases on the Web pointing to publications co-authored by Ted Kaptchuk, who has NO medical training or credentials,

http://www.sciencebasedmedicine.org/index.php/dummy-medicine...

the statements typically found in those articles, such as "Recent research demonstrates that placebo effects are genuine psychobiological phenomenon [sic] attributable to the overall therapeutic context, and that placebo effects can be robust in both laboratory and clinical settings" are untrue.

http://theness.com/neurologicablog/index.php/the-rise-and-fa...

"Despite the spin of the authors – these results put placebo medicine into crystal clear perspective, and I think they are generalizable and consistent with other placebo studies. For objective physiological outcomes, there is no significant placebo effect. Placebos are no better than no treatment at all."

http://www.ncbi.nlm.nih.gov/pubmed/20091554

"We did not find that placebo interventions have important clinical effects in general. However, in certain settings placebo interventions can influence patient-reported outcomes, especially pain and nausea, though it is difficult to distinguish patient-reported effects of placebo from biased reporting. The effect on pain varied, even among trials with low risk of bias, from negligible to clinically important. Variations in the effect of placebo were partly explained by variations in how trials were conducted and how patients were informed."

Fabrizio Benedetti, a co-author of one of the most cited papers who is also a medical doctor, sums up his view this way: "I am a doctor, it is true, but I am mainly a neurophysiologist, so I use the placebo response as a model to understand how our brain works. I am not sure that in the future it will have a clinical application."

http://www.brainsciencepodcast.com/storage/transcripts/year-...

To sum up, despite claims to the contrary by a person without medical training who is often covered by the lay press, the best-considered view among medical practitioners with clinical experience is that the placebo response has no clinical application.