How come even bright people can be 'fooled' by placebos?


The power of something that is 'just' in ones mind

The ability to respond to a placebo is something that many believe is a mark of gullibility and something that others may be capable of -- certainly not oneself. A humorous and very illustrative example of this bias -- and an example of just how unconsciously powerful a placebo can be -- comes from a Johns Hopkins neurosurgeon and placebo researcher (James Campbell), who tells of a mentor's anecdote that was a seminal influence on Campbell's attitude toward placebos [Clark 2003]: "My advisor [in medical school] was William Collins, then chief of Neurosurgery at Yale. He liked to recall an incident in the Korean War when he was working nearly night and day as a military surgeon. surgeon.operating Though he developed appendicitis and had surgery, he felt obligated to return to the Operating Room only a few hours later. His postoperative pain was terrible; he insisted on a shot of morphine. But the nurse said she'd already given him all he could [safely] have. Collins said she 'damn well better give him the morphine' or else.... Nurse preparing injection So he got the shot, noted prompt relief and continued work. doctor viewing chart.commons.jpg The next day, after a restful sleep, he looked over his [own medical] records and was flabbergasted to find he'd merely gotten saline [salt water]. At first he was disbelieving, but it became quite clear [that his body had produced a placebo response and] that the placebo effect was enormously powerful."

How could a placebo do that?

'Placebos' were originally Latin 12th century prayers for the dead [Brown 1997], so the word's connotation for medical use could only have improved from that point. Within the last 40 years, the definition of placebo has evolved one that is way off-course biologically, ie, 'something without benefit given by a doctor only to please the patient', into the more concise but still off-course 'treatment lacking biologic activity.' Now we have scientific means of measuring what happens in the body when either a traditional medical treatment or a placebo treatment is given, and we can see that visible, quantifiable, and healthful changes occur for both placebo and traditional treatments.
The parts of the brain that most consistently show healing-related changes during placebo treatments for pain, for Parkinson's disease, for depression, and for many other conditions, are the prefrontal cortex, the limbic and paralimbic system, the striatum, and the brainstem [Mayberg et al. 2002][Leuchter et al. 2002]. The laboratory methods that have been used to quantify the changes are PET (Positron Emission Tomography) imaging, fMRI (functional Magnetic Resonance Imaging), Quantitative ElectroEncephaloGraphy, analyzing chemicals in the blood, analyzing chemicals in the fluid from the spinal cord, and measuring agility of movement:
PET image from [de la Fuente-Fernandez et al. 2002] fMRI -- functional Magnetic Resonance Imaging (Petrovic et al. 2002) Quant-EEG: Quantitative ElectroEncephaloGraphy (Leuchter et al. 2002) analyzing chemicals in the blood (Amanzio et al. 1997) chemicals in the fluid from the spinal cord [Benedetti et al. 2003] measuring agility of movement (Benedetti et al. 2003)

These means are used not only to discern which brain areas are involved, but also to discover why some people respond to placebo treatment for a given disease while others do not [Petrovic et al. 2002]. For those who respond to placebos for pain, for instance, the average placebo has been found to be equivalent to about 5 mg of morphine [Petrovic et al. 2002]

But for people who do respond to placebos, there is still a benefit to be had from commercial drugs. As classical conditioning theory predicts, a placebo which looks identical to a treatment that is respected by the patient AND which is interspersed or mixed in with the respected treatment, will induce a placebo response more potent than if the same placebo were given without the traditional drug [Mayberg et al. 2002] [Benedetti et al. 2003]. since the placebo 'effect' is the body's response to a specific set of conditions, the term among researchers on the subject is 'the placebo response' (instead of 'effect').

The physiological changes induced by a placebo response are as varied as the illnesses or type of pain that they address, and scientists have only recently begun to discover the molecular mechanisms behind each fo those changes, illness by illness. Their workings are as complex as those of the commercial drugs which induce the same effect.

The illnesses or conditions that up to now have been most quantitively tested and documented for mechanisms, differences, and commonalities of placebo response are Parkinson's disease, depression, and pain. As awareness grows on how systemic the placebo response is, more and more testing is beginning to be carried out for placebo responses to hormonal and homeostatic (internal equilibrium) states [Benedetti et al. 2003] [Pollo et al. 2003] [Johansen et al. 2003], as well as for responses to illnesses [Vase et al. 2003] [Dickerson et al. 2003].

More: How could a placebo for a painkiller actually kill pain?

hand with pill


[Amanzio et al. 1997] Amanzio M, Benedetti F: Neuropharmacological dissection of placebo analgesia: expectation-activated opioid systems versus conditioning-activated systems. Journal of Neuroscience 1997; 19(1): 484-494.

[Benedetti et al. 2003] Benedetti F et. al.: Conscious expectation and unconscious conditioning in analgesia, motor, and hormonal placebo/nocebo responses. J Neuroscience 2003; 23(10): 4315-4323

[Brown 1997] Brown WA: The best medicine? Psychology Today 1997; 30(5): 56-63

[Clark 2003] Clark J: Putting placebo in its place: how to tell when reality’s more than virtual. Brain Waves: John Hopkins Neurology and Neurosurgery [online newsletter] 2003; 16(1) at

[de la Fuente-Fernandez 2002] de la Fuente-Fernandez R, Stoessl AJ: The placebo effect in Parkinson's disease. Trends in Neuroscience 2002; 25(6):302-306

[Dickerson et al. 2003] F.Dickerson, J.Boronow, C.Stallings, B.Lee, R.Agarwal, W.Fenton, R.Yolken: Placebo response in a double-blind therapeutic supplementation trial in stabilized outpatients with schizophrenia. Schizophrenia Research 2003, Volume 59, Issue 1, Pages 97-98

[Johansen et al. 2003] Johansen O, et. al.: Placebo and Nocebo Responses, cortisol, and circulating beta-endorphin. Psychosomatic Medicine 2003; 65: 786-790

[Leuchter et al. 2002] Leuchter F et. al.: changes in brain function of depressed subjects during treatment with placebo. Am J Psychiatry 2002; 122-129

[Mayberg et al. 2002] Mayberg HS et. al.: The functional neuroanatomy of the placebo effect: Am J Psychiatry 2002; 159:728-737

[Petrovic et al. 2002] Petrovic P et. al.: Placebo and opioid analgesia – imaging a shared neuronal network. Science 2002; 295(5560): 1737-1740

[Pollo et al. 2003] Pollo A et. al.: Placebo analgesia and the heart. Pain 2003; 102:125-133

[Vase et al. 2003] Vase L et. al.: The contributions of suggestion, desire, and expectation to placebo effects in irritable bowel syndrome patients. Pain 2003; 105(1-2): 17-25

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