The nocebo effect: How your own expectations can make you sick

Less well-known than the placebo effect yet just as remarkable: the nocebo effect causes you to experience more complaints because of negative expectations of a drug or your health.

This post is also available in Dutch.

At the end of the nineties, a group of Belgian children experienced stomach aches after drinking coca cola, which was broadly discussed in the media. The following weeks, hundreds of children throughout Belgium fell ill after drinking coca cola. However, no toxins were found in the drink, and the children were medically fine. The children probably fell ill because of the nocebo effect: because of the media attention, they strongly expected to fall ill after drinking cola, so that’s what they did. A most remarkable phenomenon: how can just merely expectations influence your experience, or even make you sick? And can you counter this effect?

The nocebo effect is the evil cousin of the placebo effect. You have probably heard of the placebo effect before. It causes people to experience a positive effect on their illness or their mood and reduce their complaints after taking a fake drug. The nocebo effect has the opposite effect: having negative expectations can lead to more physical complaints. If, for example, a doctor tells you explicitly about certain possible side effects, there is a greater chance that you will actually experience them.

Expectations influence your experiences

Just as with the placebo effect, previous experiences, written texts (such as a medicine information leaflet), or information obtained from the media, cause you to form expectations. These expectations can in turn affect the way you experience something, as is shown in brain research. This research shows that when someone experiences the nocebo effect, brain areas that form expectations make connections with the brain areas involved in experiencing pain and other sensory observations. So, you can experience pain or sensations that are not actually ‘real’.

One such example comes from Austrian research: participants smelled odourless water while they lay down in an MRI scanner. However, the researchers told the participants they would smell a bad odour. Even though the participants could not actually smell any odour, the brain areas that are normally active when you sense odour, were activated. Next, 76% of the participants indicated that they smelled the bad odour.

Can you counter the nocebo effect?

As shown in the Austrian study, not everyone is equally susceptible to the nocebo effect. It is not entirely clear why some people are more susceptible than others. It is likely that your personality plays a part: People who are pessimistic, introvert and/or quickly anxious, are more susceptible to the nocebo effect. Also, people who are afraid of experiencing side effects or catching a disease, will do so more easily.

Thus, expectations can have significant impact on your experiences, either positively or negatively. If you are susceptible to this, adopting a positive attitude will help. Also, being aware of the existence of this effect causes you to experience it less. By reading this blog, the odds of experiencing a nocebo effect have already decreased!

Keep reading?

A previous blog on the placebo-effect:


Author: Judith Scholing
Buddy: Marlijn ter Bekke
Editor: Felix Klaassen
Translation: Wessel Hieselaar
Editor translation: Ellen Lommerse

Image by JESHOOTS via Pexels

1 thought on “The nocebo effect: How your own expectations can make you sick

  1. I find particularly thought provoking about Italian study is that it demonstrates the existence of a “social nocebo” – where our friends, colleagues, family members, and doctors can communicate negative expectations that result in a biological response. The propagation of negative and positive expectation could be very important in illness in general and in the generation of pathology or disease. More info you will find here – net-bossorg/the-power-of-the-placebo-effect-by-randy-baker

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