The effect of social exclusion on pain perception and heart rate variability in healthy controls and somatoform pain patients

Objectives - The overlapping neural networks of social and physical pain have been investigated intensively in recent years. It was postulated that triggering social pain might result in greater physical pain. Nonetheless, how this affects somatoform pain disorder has not yet been considered. Since an increased pain processing activity is reported in these patients, the investigation of social exclusion and its effect on this group seems interesting. Hence, the aim of this study was to compare the influence of social exclusion on healthy controls and patients with somatoform pain disorder. Methods - Nineteen patients with somatoform pain disorder and 19 healthy controls were examined. Cyberball, a virtual ball-tossing paradigm, was used to experimentally induce social exclusion and inclusion. To measure effects on pain perception, pressure pain thresholds and heart rate variability (HRV) were recorded after each round of cyberball. Demographic data, pain medication, and potential psychosocial moderators were collected by questionnaires. Results - After social exclusion, pressure pain thresholds were significantly reduced in healthy controls (p < 0.01) as well as somatoform pain patients (p < 0.05), while HRV increased only in patients with somatoform pain disorder (p < 0.05) indicating increased parasympathetic activity. Conclusion - This study is the first to analyse the effects of social exclusion on pain perception in somatoform pain disorder. While the reduction in pressure pain thresholds is in line with the social pain literature, the effects on HRV could be interpreted as a form of pain regulation mechanism. However, further research is needed to investigate the role of parasympathetic activity in socially excluded somatoform pain patients.