Negative expectations are twice as strong as positive ones

Spektrum der Wissenschaft

4.6.2025

Translation: machine translated

Worries and fears increase pain significantly more than hope and positive assumptions reduce it. How doctors communicate is therefore crucial to the success of treatment.

Fears outweigh hopes. This summarises the central finding of a study from the University of Duisburg-Essen. In an experiment involving more than 100 people, a team from the Collaborative Research Centre Treatment Expectation led by neurologist Ulrike Bingel deliberately manipulated the expectations of a heat stimulus on the forearm and of a supposedly pain-relieving or pain-intensifying stimulation. This sham treatment was carried out using a transcutaneous electrical nerve stimulation device (TENS).

The placebo effect is well known: Positive expectations alone can already alleviate symptoms. The opposite nocebo effect is also well documented: The assumption that a therapy will not help anyway or will bring unpleasant side effects can diminish the success of an actually effective treatment or even ruin it. The scientists now asked themselves the question: which of the two effects is stronger?

Nocebo beats placebo

The result: both placebo and nocebo effects were strong and could still be detected a week after the actual experiment. However, negative expectations increased pain significantly more than positive expectations alleviated it. Although the induced heat stimulus was always the same during the test phase, the perceived pain (on a scale of 0 to 100) increased by an average of eleven points with a negative expectation, while a positive expectation only reduced it by around four points. Even a week later, a fear still had around twice the effect of a hope.

«People apparently tend to expect the worst - and this is also reflected in pain processing», explains Ulrike Bingel in a press release. This seems to make sense from an evolutionary point of view, as it means we are better prepared for potential threats. However, this is a hindrance to the success of medical treatment. The findings illustrate how powerful the placebo and nocebo effects are - and the extent to which information about a therapy influences patients' expectations.

Communication is the key

Good communication is therefore crucial. When talking to their patients, healthcare professionals should not only encourage hope that the therapy will be successful. It could be even more important to reduce worries and fears in this regard. «Positive wording, avoiding unnecessary emphasis on side effects and building a trusting relationship can reduce the risk of nocebo reactions», emphasises Ulrike Bingel.

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