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What Is The Opposite Of The Placebo Effect?

What Is The Opposite Of The Placebo Effect?

The placebo effect is when someone takes a chemically inert pill (dummy drug) or has a sham surgery/treatment but exhibits perceived or actual improvement in a medical condition. Is there an opposite of this effect?

What Is The Opposite Of The Placebo Effect?

It’s called the nocebo effect. The nocebo effect is when a person experiences harmful, unpleasant, or undesirable side effects after a placebo medical treatment. These effects are not chemically generated and are only due to a person’s negative belief or expectation that the fake treatment or drug will produce bad side effects. Yet despite not getting as much attention in the medical field or in the media (when compared to the placebo effect), it afflicts roughly the same number of people as the placebo effect.

History Of The Term

The name ‘nocebo’ was coined by Mr. Walter Kennedy in 1961. He used it to describe results caused by negative reactions of a placebo treatment. He chose the word because it is Latin for “I will harm”, whereas Placebo is Latin for “I will please”. This is why when someone is given phony medication and it produces a positive reaction, it’s called a ‘placebo effect’. When the opposite occurs, and bad or negative side effects occur, it is considered a nocebo result. Both of which are caused by the patient’s own expectations and not from any other outside factor. Proof that the mind is a powerful thing.

It wasn’t until the 90′s that the distinction between a placebo and a nocebo became popular. Before that, both effects were simply called ‘placebos’. Having separate names and definitions for these words still remain slightly controversial, even today. This is because it is possible to consume a placebo pill and experience both a placebo and a nocebo effect at the same time. An example of this would be a person who is given a sugar pill and told it will take away a headache, but may cause a rash. If the patient reports that it does indeed cure their headache, but now they have a rash, then it is both a placebo and a nocebo. The benefit to the distinction in having separate terms is that specific effects can now be more accurately characterized and studied.

Has Research Been Done On Nocebos?

Nocebo IinfograficResearch on nocebos has been very rare thanks to its inherent nature — the negative side effects caused by a person’s own beliefs (which can be lethal). However, there are a few documented studies. In one such study, 34 college undergrads were hooked up to a machine and told that a tiny amount of electricity would pass through their head. They were told that it would cause them to have a headache. In reality, the machine did absolutely nothing. Yet over 22 students (66%) reported having a headache while connected to the machine.

Another was done by Japanese researchers on 57 high school kids. They chose subjects who claimed to get a severe rash when exposed to lacquer trees (very similar to poison ivy). They blindfolded the boys and proceeded to brush one of their arms with the lacquer tree leaves and the other with harmless leaf. They told the students that the arm brushed with the lacquer tree was brushed by a regular leaf, and the one brushed by the regular leaf they were told was brushed by the lacquer tree leaf. Surprisingly, a rash developed on most of the boy’s arms that were brushed by the harmless leaf and the other arm that was actually brushed by the lacquer leaf was completely fine in almost every case.

It Can Be Lethal?

The nocebo effect can certainly be lethal. One notable case occurred in the late 1970s when doctors incorrectly diagnosed a man with liver cancer and told him he had a few months to live. nocebo lethalThe man died within a few months as the doctors said he would. Upon doing his autopsy though, they found the doctors had been wrong and he did not have liver cancer. Other than being dead, the man was in perfect health.

This is a large part of the reason why doctors will downplay or not tell patients when a procedure or surgery might be excessively painful. It has been found that by doing so, they severely increase the amount of pain the patients report feeling throughout the procedure. Similarly, doctors informing a patient about all the possible side effects of a particular medication seem to increase the number of side effects a patient experiences, even when given placebos. By not being 100% honest with the patients about the negative side effects, it usually works out better for the patients because of the nocebo effect. On the other side of the coin, being extremely optimistic about the positive effects of drugs seems to greatly increase the effectiveness of medications because of the placebo effect.

Spiegel, H., “Nocebo: The Power of Suggestibility”, Preventive Medicine, Vol.26, No.5, (1997), pp.616-621.
Montgomery GH, Kirsch I (1997). “Classical conditioning and the placebo effect”. Pain 72 (1–2): 107–13.
Stewart-Williams (2004). “The placebo effect: dissolving the expectancy versus conditioning debate”. Psychol Bull 324–40.


  1. pepsi813

    I never thought about negative placebo effects before… Crap, now that I know, will I be susceptible? Ignorance is bliss.

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