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nocebo and nocebo effect

Research has...shown that the nocebo effect can reverse the body's response to true medical treatment from positive to negative.  (Root-Bernstein 1998)

A nocebo (Latin for "I will harm") is something that should be ineffective but which causes symptoms of ill health. A nocebo effect is an ill effect caused by the suggestion or belief that something is harmful. The term 'nocebo' became popular in the 1990s. Prior to that, both pleasant and harmful effects thought to be due to the power of suggestion were usually referred to as being due to the placebo effect.

Because of ethical concerns, nocebos are not commonly used in medical practice or research. Thus, it is not unexpected that the nocebo effect is not well-established in the scientific literature. However, there are some anecdotes and some studies that are commonly appealed to in the literature to support its validity.

More than two-thirds of 34 college students developed headaches when told that a non-existent electrical current passing through their heads could produce a headache.

"Japanese researchers tested 57 high school boys for their sensitivity to allergens. The boys filled out questionnaires about past experiences with plants, including lacquer trees, which can cause itchy rashes much as poison oak and poison ivy do. Boys who reported having severe reactions to the poisonous trees were blindfolded. Researchers brushed one arm with leaves from a lacquer tree but told the boys they were chestnut tree leaves. The scientists stroked the other arm with chestnut tree leaves but said the foliage came from a lacquer tree. Within minutes the arm the boys believed to have been exposed to the poisonous tree began to react, turning red and developing a bumpy, itchy rash. In most cases the arm that had contact with the actual poison did not react." (Gardiner Morse, "The nocebo effect," Hippocrates, November 1999, Hippocrates.com) [please see reader comments]

In the Framingham Heart Study, women who believed they are prone to heart disease were nearly four times as likely to die as women with similar risk factors who didn't believe.* (Voelker, Rebecca. "Nocebos Contribute to a Host of Ills." Journal of the American Medical Association 275 no. 5 (1996): 345-47. ) [Of course, one might argue that the women in both groups had good intuitions. The objective risk factors may have been the same, but subjectively the women knew their bodies better than the objective tests could reveal.]

C. K. Meador claimed that people who believe in voodoo may  actually get sick and die because of their belief ("Hex Death: Voodoo Magic or Persuasion?" Southern Medical Journal 85, no. 3 (1992): 244-47).

"In one experiment, asthmatic patients breathed in a vapor that researchers told them was a chemical irritant or allergen. Nearly half of the patients experienced breathing problems, with a dozen developing full-blown attacks. They were “treated” with a substance they believed to be a bronchodilating medicine, and recovered immediately. In actuality, both the “irritant” and the “medicine” were a nebulized saltwater solution."*

Double-blind, controlled studies have repeatedly shown that electro-sensitives can't tell the difference between genuine and sham electro-magnetic fields (EMFs).1, 2 For example, a research team in Norway (2007) conducted tests using sixty-five pairs of sham and mobile phone radio frequency (RF) exposures. "The increase in pain or discomfort in RF sessions was 10.1 and in sham sessions 12.6 (P = 0.30). Changes in heart rate or blood pressure were not related to the type of exposure (P: 0.30–0.88). The study gave no evidence that RF fields from mobile phones cause head pain or discomfort or influence physiological variables.

About 20% of patients taking a sugar pill in controlled clinical trials of a drug spontaneously report uncomfortable side effects — an even higher percentage if they are asked.*

Arthur Barsky, a psychiatrist at Boston's Brigham and Women's Hospital, found in a recent review of the nocebo literature that patient expectation of adverse effects of treatment or of  possible harmful side-effects of a drug, played a significant role in the outcome of treatment (Barsky et al. 2002).

Since patients' beliefs and fears may be generated by just about anything they come in contact with, it may well be that many things that are unattended to by many if not most physicians, such as the color of the pills they give, the type of uniform they wear, the words they use to give the patient information, the kind of room they place a patient in for recovery, etc., may be imbued with rich meaning for the patient and have profound effects for good or for ill on their response to treatment.

See also placebo effect.

reader comments

further reading

books and articles

Barsky, Arthur J., M.D. et al. "Nonspecific Medication Side Effects and the Nocebo Phenomenon," Journal of the American Medical Association, Vol. 287 No. 5, February 6, 2002.

Engel, Linda W. et al. The Science of the Placebo - Toward an Interdisciplinary Research Agenda ( BMJ Books, 2002).

Morse, Gardiner. 1999. "The Nocebo Effect - Scattered studies suggest that negative thinking can harm patients’ health," Hippocrates, November, Vol. 13,  No. 10.

Root-Bernstein, Robert and Michele. Honey, Mud, Maggots and Other Medical Marvels: The Science Behind Folk Remedies and Old Wives' Tales  (Houghton Mifflin Co., 1998).


The nocebo response This article was first printed in the March 2005 issue of the Harvard Mental Health Letter.

"The Nocebo Effect: Placebo's Evil Twin," by Brian Reid Special to The Washington Post, April 30, 2002

Is there an "anti-placebo" effect? The Straight Dope, 28-Jan-2000

"The Nocebo Effect: Do No Harm" by Morton Kasdan, M.D. et al., Journal of Southern Orthopaedic Association Summer 1999.   "The nocebo effect creates negative health expectations that are detrimental to the outcome of the patients recovery. During the 1960's the nocebo effect was first described as the "voodoo death".  In some regions of the world the "medicine man" used the nocebo effects to cause death by fright. More recently, this type of effect is described as psychogenic illness or mass hysteria"   Epidemics usually start by an individual, in the work place an epidemic is commonly triggered by an odor. If one or more workers become sick, attributing symptoms to the smell, anxiety spreads throughout the workplace and fuels the spread of illness. Nocebo means "I will harm" in contrast to the placebo "I will please". For my study with pain management the nocebo effect helps me to understand how a diagnosis can harm or help a patient with their recovery. In the diagnosis of pain some may say a more general diagnoses such as chronic pain has a lesser effect on the patients initial response and a greater effect on the patients recovery. Where as with a diagnosis of Reflex Sympathetic Dystrophy, this diagnosis may lead a patient into a negative frame of mind in the initial and create long lasting symptoms and recovery time. Both diagnosis are for pain and both lack objective findings for the pain. We learned at a young age how to cope with symptoms and feelings, i.e.. children get the flu they whine for assistance and they get a reaction. We learn to play the patient role, and the placement of a name upon a concept, whether real or imaginary, brings it into clinical existence. The words used in medicine largely influence the diagnosis they describe. I guess we could say mind over matter comes into play when dealing with what a diagnosis really is saying or what we think it is saying.

'Nocebo Effect' May Explain Some Drug Side Effects Feb 7, 2000 by Merritt McKinney

Expectations about your health or illness can cause reality to follow suit by Susan McCarthy, Salon.com, 7-15-1999

How the Media and Lawyers Stir Up False Illness by Michael Fumento

news stories

The contagious thought that could kill you "Today, the nocebo is perhaps most visible in such controversial disorders as “wind turbine syndrome” (sickness and insomnia from wind farms, most common in Canada) and “electro-sensitivity” – an allergic reaction to mobile phone signals and wi-fi. Some sufferers even resort to sleeping in metal cocoons to avoid the constant ringing in their ears. Yet dozens of experiments have shown that people are just as likely to report the same symptoms when they are exposed to a sham transmitter that doesn’t actually emit any electromagnetic waves."

People who see themselves as unlucky should stay indoors on Friday the 13th, according to new research.


All bow before the mighty power of the nocebo effect by Ben Goldacre. This is the amazing world of the nocebo effect, where negative expectations can induce unpleasant symptoms, in the absence of a physical cause.

New Placebos Have Side Effects Too So, was the "nocebo effect" really making people feel worse?

Last updated 27-Oct-2015

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