The Power of Placebo Effect

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.

Using brain scans the University of Michigan Health System scientists found that placebo treatment triggers the brains 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 feelings of pain.

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 behavioral economist at Duke University.

Researchers at the Massachusetts Institute of Technology used a standard protocol for administering light electric shock to participants’ wrists to measure their subjective rating of pain. The 82 study participants were tested before taking the placebo and after. Half the participants were given a brochure describing the pill as a newly-approved pain-killer which cost $2.50 per dose and half were given a brochure describing the pill as marked down to 10 cents. In the full-price group, 85% of participants experienced a reduction in pain after taking the placebo. In the low-price group, 61% said the pain was less.

4 The power of healing ritual

Sham devices seem to be more effective than sham pills.

While researchers typically use placebos in clinical trials to test the effectiveness of a real treatment, this experiment pitted one placebo against 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.

These findings suggest 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 did, in fact, seem to improve lung function.


Placebo effect can last for years

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

The 2-year study7, conducted at 28 centers in Canada, involved 613 patients who were given either the drug Proscar (finasteride) or a placebo. Doctors found that the 303 men on the placebo pills really were doing better, even though their prostates had grown, on average, by 8.4%. Although an enlarged prostate can impede urine flow, urine flow was improved for 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 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 anti-depressants 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 an antidepressant, does their 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 studies (16,364 patients) for 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 bigger and more dramatic the patient perceives the intervention to be, the bigger the placebo effect. Big pills have more than small pills, injections have more than pills and surgery has the most of all.

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.

In an international clinical trial of 7,599 heart failure patients1, the researchers found that good adherence was associated with similar lower mortality rates for both the placebo and an angiotensin receptor blocker (ARB), a medication used to relax and dilate blood vessels, 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

Compared to real acupuncture, placebo acupuncture is associated with significantly higher overall pregnancy rates among women undergoing in-vitro fertilization (IVF), according to the University of Hong Kong study15.

The researchers 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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  • 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.
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  • 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.
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Last updated: February 18, 2016
Created: February 18, 2016


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