How expectations influence stomach ache – and how the experience of pain changes treatment expectations

Anyone who’s ever had a bad stomach ache knows that internal (so-called “visceral”) pain, which originates from the organ systems, differs in lots of ways from external (“somatic”) pain, such as from cuts and grazes. Visceral pain, as is typical, for instance, with irritable bowel syndrome, is usually harder to pinpoint, its causes are more difficult to identify, and sufferers often have additional symptoms. However, visceral and somatic pain, and above all their treatments, have one thing in common: Both are closely related to the sufferer’s expectations.

Stress and negative mood have a particularly intensive effect on visceral pain

In Project A04, we are investigating these complex associations with the aim of using our findings to improve treatment approaches for various chronic pain disorders. To do so, we can build on the findings from the first funding period of the CRC, in which we demonstrated that visceral pain in particular triggers anxiety and is strongly influenced by negative expectations. Stress and negative mood – as is the case, for instance, with depression – likewise seem to have an especially intensive impact on visceral pain. Demonstrating how emotional factors also play a strong role in somatic pain, we conducted a study in which chronic back pain patients receiving open-label placebos (OLP) reported an improvement not only in their pain but also in their mood.

Differences and interactions between visceral and somatic pain

In the second funding period, we will be analysing these phenomena in more detail: How do expectations and mood influence the effectiveness of treatment for visceral and somatic pain, and vice versa, how do treatment experiences influence expectations of future treatment attempts? Are there differences between somatic and visceral pain? How do these associations develop over the course of various different experiences of pain, and in particular over the course of treatment? And how do visceral and somatic pain interact with each other?

In Project A04, we are tackling these questions in experiments with healthy participants experiencing acute pain within different treatment approaches. Besides standardized surveys on pain perception, we will also measure psychophysiological parameters like heart rate variability and hormone concentrations. Additionally, we will draw on the data on participants’ brain activity using functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) as well as questionnaire data from our overarching projects Z02 and Z03.