A new study from our Collaborative Research Center shows: Negative expectations have a stronger effect and last longer than positive ones. This result is of great importance for communication between doctors and their patients.
It's a kind of self-fulfilling prophecy: if we truly believe that a treatment will help, it is more likely to work. Conversely, if we fear that the treatment will be ineffective and cause unpleasant side effects, this is often exactly what happens.
This phenomenon is particularly common and well-studied in the case of pain: positive expectations can alleviate pain and increase the effect of a painkiller – this is the placebo effect. Negative expectations, on the other hand, often intensify the pain and can nullify the effect of even highly potent painkillers – this is known as the nocebo effect.
In experiments, nocebo effects are stronger than placebo effects
But which of these effects is stronger? Unfortunately, it is probably the nocebo effect, as a study from projekt A01 of our CRR 289 shows. In an experiment, a research team led by Prof. Ulrike Bingel at the University of Duisburg-Essen exposed 104 healthy volunteers to short-term heat pain. The researchers specifically influenced the participants' expectations and treatment experiences of a sham nerve stimulation and then investigated how strongly these affected subsequent test phases on the same day and after one week. In these test phases, all participants received equally strong pain stimuli - but associated with different expectations: positive, negative or neutral. The pain stimuli were rated on a scale of 0–100.
The exciting result: negative expectations had a stronger and more lasting influence on the sensation of pain than positive ones. On average, those with negative expectations rated subsequent pain around 11 points higher than those with no specific expectations. A positive expectation, on the other hand, only reduced the pain rating by around 4 points. (Here is the link to the original publication.)
The effect of negative expectations is greater - even in the long term
The effect of negative expectations was twice as strong as that of positive expectations - even though the pain induced was the same for all participants. Only the expectations were different. But how long does this effect last?
To test this, all participants received the same pain stimulus again in the second session one week later. The effect remained similar: the nocebo effect meant that the people with negative expectations rated the pain about 9 points higher than those in the control group without expectations. The placebo effect, on the other hand, resulted in the pain being perceived as 4.6 points lower.
"Better safe than sorry": Why do people expect the worst?
“People apparently tend to expect the worst - and this is also reflected in the way they process pain,” explains Prof. Dr. Ulrike Bingel, neurologist and head of the Interdisciplinary Center for Pain Medicine at Essen University Hospital. The reason for this could lie in human evolution, suspects Dr. Katharina Schmidt from Bingel's team, who was also involved in the study: “This behavior corresponds to a ‘better safe than sorry’ strategy.” It is possible that humans have evolved to be better prepared for potential threats - and therefore give more weight to negative expectations.
“This is very important for clinical practice,” explains neurologist Bingel. In everyday life, doctors often focus on promoting positive expectations. "However, our study shows that it is at least as important to avoid unintended negative expectations," says Bingel. Healthcare professionals should be aware that the way they provide information about treatments can strongly influence patients' reactions to them – in both a positive and negative sense.
“Nocebo effects can be prevented by simple and effective strategies to improve communication between patients and doctors,” adds Bingel: "Positive wording, avoiding unnecessary emphasis on side effects and building a trusting relationship can reduce the risk of nocebo reactions. At a time when cost efficiency in healthcare is critical, avoiding nocebo effects should be a key strategy to improve treatment outcomes."
Foto: SFB/TRR 289