Negative Expectations Influence Pain More Strongly and Persist Longer Than Positive Expectations

Recent research highlights that negative expectations can significantly exacerbate perceived pain and have more durable effects compared to positive expectations, which tend to provide only modest relief. Published as a reviewed preprint in eLife, this study investigates how the human mind differentially processes positive and negative anticipations in the context of pain perception.

The study stems from the understanding of placebo and nocebo effects—phenomena where expectations influence symptom experience. A placebo effect can make individuals feel better simply because they believe a treatment will help, even if it is inactive. Conversely, a nocebo effect leads to worse outcomes driven by negative expectations, even without physical causes.

Lead researcher Katharina Schmidt, a senior postdoc at the University Duisburg-Essen, explained that while many studies have explored these effects individually, few have directly compared their strength and longevity over time within the same subjects. Their goal was to determine whether negative expectations exert a more potent and lasting influence on pain than positive ones, which is especially relevant in clinical settings where healthcare providers' communication shapes patient outcomes.

The experiment involved 104 healthy volunteers who participated in two sessions spaced one week apart. During the first session, participants were subjected to brief heat pains paired with verbal suggestions and a sham nerve stimulation device designed to induce expectations of pain relief (placebo), increased pain (nocebo), or no change (control). Carefully calibrated heat stimuli were used, with expectations reinforced to influence pain ratings, which were assessed on a scale from 0 (no pain) to 100 (unbearable pain).

Results indicated that both placebo and nocebo suggestions affected pain perception, with the nocebo effect being notably stronger. On the first day, nocebo participants reported an average increase of 11.3 points in pain ratings compared to the control, while placebo participants experienced only a 4.2-point reduction. In the second session, conducted a week later, these effects persisted, with nocebo responses remaining more pronounced: an 8.9-point increase versus a 4.6-point decrease for placebo.

This pattern suggests that humans are more prone to expect and experience worse pain outcomes than better ones, possibly due to an evolutionary 'better-safe-than-sorry' response aimed at threat detection. Interestingly, prior pain experience influenced subsequent responses; individuals who showed strong effects initially tended to show similar responses later. Psychological traits also played a role, with more sensitive individuals or those perceiving the experimenter as highly competent being more susceptible to negative suggestions.

The researchers emphasized that this study was conducted with healthy volunteers using experimental pain stimuli, and further research is needed to understand how these findings translate to clinical contexts. Senior author Ulrike Bingel noted that nocebo responses tend to be stronger and more persistent than placebo effects, highlighting the importance of communication in clinical practice. They suggest strategies such as positive framing, minimizing side effect emphasis, and fostering trust to mitigate nocebo responses.

These insights underscore the necessity to carefully manage patient expectations to improve treatment outcomes and reduce unnecessary suffering induced by negative anticipations.

(Source: https://medicalxpress.com/news/2025-04-negative-stronger-longer-effects-pain.html)