The Power of Placebo Effect

by eMedExpert staff
Medical references reviewed: August, 2018

Placebo pill

The power of the mind can heal the body.

In clinical trials placebo are used to validate whether a tested medicine has any healing effect beyond that which occurs a certain percentage of time when people take an inert pill. A patient's belief in a pill – a supposed medicine, but chemically innocuous – is thought to activate their body's healing powers.

For years, scientists have looked at the placebo effect as just a figment of overactive patient imaginations. However, by now researchers have discovered that the placebo effect is not "all in patients' heads" but rather, in their brains.

Placebo effect is a wonderful presentation of the power of our minds and our belief systems. It proves that our thoughts may actually interact with the brain in a physical way.

eMedExpert has looked through scientific research and found a number of quite interesting data about placebos that have been published in the medical literature.

1Information provided to patients influences placebo and drug effects

There was an interesting study16 in which participants with migraine attacks received either placebo or Maxalt (rizatriptan) given under 3 information conditions:

  • negative (told placebo, 0% chance of receiving an active medication)
  • neutral (told Maxalt or placebo, 50% chance of receiving a medication)
  • positive (told Maxalt, 100% certainty of receiving a medication)

When patients took Maxalt that was labeled "placebo" (a treatment that theoretically is ineffective), the results did not differ from those in patients given placebos deceptively labeled "Maxalt" (purely expectation effect). And when Maxalt was rightly labeled "Maxalt" its migraine relieving efficacy increased by 50%.


2 Placebo effect produces real pain-killers

Significant placebo effect has been seen in the treatment of pain.

Medical researchers have found, for example, that a placebo given for pain may be as effective as 8 mg of morphine (a modest dose)2.

Researchers the University of Michigan Health System discovered that placebo treatment triggers in the brain the production of natural painkillers, called endorphins3. This study provides the first direct evidence that the brain's own pain-fighting chemicals play a role in the pain-related placebo effect – and that this response corresponds with a reduction in pain perception.

3 Costly placebo works better than cheap one

A 10-cent pill doesn’t kill pain as well as a $2.50 pill, even when they are identical placebos, according to a provocative study by Dan Ariely4, a Professor of Psychology and Behavioral Economics at Duke University.

MIT researchers conducted the following study. They measured subjective rating of pain of 82 participants by applying light electric shock to their wrists. Half of the participants were given placebo pill described as a new pain killer costing $2.50 per dose and the other half

received the same pill, only they were told that it costs only 10 cents. After taking the medicine, rating of pain has been measured once again. In the "expensive" group, 85% of participants reported a reduction in pain and in the "discount" group, 61% said the pain was less.

4 The power of healing ritual

Sham devices seem to be more effective than sham pills.

While scientists usually use placebo in clinical trials to test the effectiveness of a real treatment, this experiment compared one placebo to another. Researchers investigated whether a sham acupuncture device has a greater placebo effect than an inert pill5. The results of this study show that the placebo effect varies by type of placebo used. In the second phase of the study, participants receiving sham acupuncture reported a more significant decrease in pain and symptom severity than those receiving placebo pills for the duration of the trials.

This experiment demonstrates that the medical ritual of a device can deliver an enhanced placebo effect beyond that of a placebo pill.

5 Strong placebo response in asthma

Placebo effect is often observed in asthma patients – that is, they show an improvement in their condition even when they just think they are being treated.

Interestingly, the patients not only report an improvement in their disease, but objective tests indicate an improvement as well, according to the report in the Journal of Allergy and Clinical Immunology6.

Previous reviews have suggested that placebo benefits are restricted to subjective responses, like pain, but are ineffective for objective physiological outcomes. Researchers from the University of California, San Francisco, investigated whether there was a placebo response in objective measures of lung function in 55 patients with asthma.

The results of the methacholine challenge test, which gauges how well a particular drug opens constricted airways, showed that placebo can actually improve lung function.


Placebo effect can last for years

The brain's power to make people feel better can last for years.

Canadian scientists7 conducted a two-year experiment in which patients received either the medication Proscar (finasteride) or a placebo. Doctors found that majority men on the placebo pills really were doing better, even though their prostates had grown. It is well known that enlarged prostate can impede urine flow. But surprisingly urine flow was improved in the men taking the placebo. Some participants, continuing to do very well on placebo, didn’t want to stop taking the pills.

The placebo effect can last for a long time if the three necessary conditions are maintained8:

  • beliefs and expectations of patients
  • beliefs and expectations of doctors
  • a good relationship between them

7Tremendous placebo effect in depression

The placebo effect is particularly apparent in illnesses that have a strong psychological component, such as anxiety and depression. Placebo help nearly half of depressed people get better.

In 2009 researchers analyzed 12 studies which included 2,862 children (median age 12.3 years) who were randomized to either an antidepressant or placebo9. The antidepressant medications in those 12 studies were Prozac, Paxil, Zoloft, Lexapro, Celexa, Effexor, Remeron and Serzone. Taken together, 49% of children responded to placebo while 57% percent responded to an antidepressant. That makes for a global effect size of 8%, meaning a doctor would have to give antidepressants to 10 kids before seeing a response in one of them.

How long-lasting is this placebo effect? If a person continues receiving a placebo instead of a real antidepressant, does the depression get worse over time?

Scientists from Northwest Clinical Research Center10 analyzed research where patients were continued on placebo for more than 12 weeks and examined whether they relapsed back into depression or not. The researchers found that 79% of those receiving placebo continued to be depression-free 4 months after their initial treatment (4 out of 5 people), compared with 93% of those taking an antidepressant medication.

8 Placebo is quite effective treatment for osteoarthritis

Researchers examined the placebo effect in 198 randomized, placebo-controlled health studies involving 16,364 patients with osteoarthritis11. A wide range of treatments were involved – drugs, non-drug treatments, and surgical procedures.

The ultimate conclusion was surprising. It stated that, “Placebo is effective in the treatment of osteoarthritis, especially for pain, stiffness and self-reported function.”

Placebo was found to be effective for relieving pain, improving function, and decreasing joint stiffness associated with osteoarthritis. The size of the placebo effect was affected by the strength of the active treatment, how severe the disease was at the study onset, as well as how the placebo was administered.

Interestingly, the pain-relieving effect of the placebo increased when the placebo was given through injection.

9 Placebo surgery surprise:
fake procedures are as good as "real" surgery

Placebo surgery shows surprising results! In fact, in those studies where placebo surgery has been used, many patients receiving the placebo improved.

The study of treatments for angina pectoris (unspecified chest pain) has been particularly revealing.

In the 1950s, many physicians treated angina with ligation of the internal mammary artery. Despite claims of up to a 91% success rate, in the late 1950s, two skeptics conducted separate double-blind tests in which half the patients received skin incision, but not artery ligation12-13. In both studies, the placebo surgery proved equally effective as the ligation. And the overall rate of improvement with the placebo was 37%.

A 2002 study of arthroscopic knee surgery found that the outcomes for a placebo procedure were as good as those of the "real" surgery14.

The more serious intervention is in the eyes of the patient, the better the placebo effect is. And if we compare the placebo effects of different treatment methods, then it will look like this: surgery > injection > big pills > small pills.


10 Taking Pills, even placebo, predicts better survival in heart failure

Heart-failure patients have a better chance of survival if they’re conscientious about taking their pills, even if those pills are placebos, says a Duke University Medical Center study.

An international clinical trial of 7,599 heart failure patients1, demonstrated that good adherence to treatment plays an important role in the effectiveness of treatment. In this study good adherence was associated with similar lower mortality rates for both the placebo and angiotensin receptor blockers, when compared to patients who were not as adherent. Also, good adherence was associated with lower rates of hospitalization for both placebo and active drug.

11 Placebo acupuncture tied to higher in-vitro fertilization pregnancies

Even more incredible is that compared to real acupuncture, placebo acupuncture is associated with significantly higher overall pregnancy rates among women undergoing in-vitro fertilization, according to the University of Hong Kong study15.

The researchers at the University of Hong Kong gave real or placebo acupuncture to 370 women on the day of embryo transfer and found that 55.1% of those who received placebo acupuncture became pregnant, compared to 43.8% of those who received real acupuncture.

12 Placebo effect exists in animals

It is believed that the beneficial effect of placebo arises from a person's expectations from a treatment, rather than from the treatment itself. Animals would seem to lack the cognitive capacity to comprehend such expectations. Nevertheless, there is evidence that placebo pills may help dogs to get better17.


Hope, faith, and love work wonders.


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  • 2. Fabrizio Benedetti. The Placebo and Nocebo Effect: How the Therapist’s Words Act on the Patient’s Brain. Karger Gazette No 69
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  • 5. Kaptchuk TJ, Stason WB, Davis RB, Legedza AR, Schnyer RN, Kerr CE, Stone DA, Nam BH, Kirsch I, Goldman RH. Sham device v inert pill: randomized controlled trial of two placebo treatments. BMJ. 2006 Feb 18;332(7538):391-7.
  • 6. Kemeny ME, Rosenwasser LJ, Panettieri RA, Rose RM, Berg-Smith SM, Kline JN. Placebo response in asthma: a robust and objective phenomenon. J Allergy Clin Immunol. 2007 Jun;119(6):1375-81. PubMed
  • 7. Nickel JC, Fradet Y, Boake RC, Pommerville PJ, Perreault JP, Afridi SK, Elhilali MM. Efficacy and safety of finasteride therapy for benign prostatic hyperplasia: results of a 2-year randomized controlled trial (the PROSPECT study). CMAJ. 1996 Nov 1;155(9):1251-9. PubMed
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  • 11. Zhang W, Robertson J, Jones AC, Dieppe PA, Doherty M. The placebo effect and its determinants in osteoarthritis: meta-analysis of randomized controlled trials. Ann Rheum Dis. 2008 Dec;67(12):1716-23.
  • 12. Cobb LA. Evaluation of internal mammary artery ligation by double-blind technique. NEJM 1959; 260: 1115–1118.
  • 13. Dimond EG, Kittle CF, Crockett JE. Evaluation of internal mammary artery ligation and sham procedure in angina pectoris. Circulation 1958;18:712-3.
  • 14. Moseley JB, O’Malley K, Petersen NJ, Menke TJ, Brody BA, Kuykendall DH, Hollingsworth JC, Ashton CM, Wray NP. A controlled trial of arthroscopic surgery for osteoarthritis of the knee. NEJM 2002 Jul 11;347(2):81-8.
  • 15. So EW, Ng EH, Wong YY, Lau EY, Yeung WS, Ho PC. A randomized double blind comparison of real and placebo acupuncture in IVF treatment. Hum Reprod. 2009 Feb;24(2):341-8.
  • 16. Kam-Hansen S, Jakubowski M, Kelley JM, Kirsch I, Hoaglin DC, Kaptchuk TJ, Burstein R. Altered placebo and drug labeling changes the outcome of episodic migraine attacks. Sci Transl Med. 2014 Jan 8;6(218):218ra5. PubMed
  • 17. Muñana KR, Zhang D, Patterson EE. Placebo effect in canine epilepsy trials. J Vet Intern Med. 2010 Jan-Feb;24(1):166-70. PubMed

Last updated: January 6, 2018
Created: February 18, 2016


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