Verbal support from a stranger reduces the development of mechanical hypersensitivity: behavioural, electrophysiological evidence and the moderating role of attachment styles

Various forms of social support have been evidenced to diminish acute pain ratings and modulate physiological responses to acute pain stimuli, with adult attachment styles moderating this effect. However, only one study to date has examined the impact of the social context (using a hand-holding intervention by a romantic partner) on experimentally induced secondary mechanical hypersensitivity, a common symptom of chronic pain. Here, we aimed to discern whether structured verbal support from a stranger, a situation that perhaps better approximates a clinical context, could attenuate the development of experimentally induced secondary mechanical hypersensitivity and whether attachment styles moderate this effect. Mechanical hypersensitivity was induced using a well-established electrical stimulation protocol, in forty-four healthy female participants who were randomly assigned to either a support group or an alone group. Participants in the support group received structured verbal support from a stranger during the electrical stimulation. The effect of the electrical stimulation on skin conductance level and cortisol responses was measured to examine the role of the sympathetic and HPA systems, respectively. Additionally, cortical responses to mechanical stimulation were measured before, and after the electrical stimulation to assess differences in cortical responses. Findings reveal that verbal support attenuated not only the perceived intensity and unpleasantness of hypersensitivity but also the late part of the cortical response to pinprick stimulation. Attachment anxiety moderated subjective ratings as well as the spread of hypersensitivity and attachment avoidance moderated the subjective ratings. Social support had no impact on stress responses to the electrical stimulation

The Role of Pain Expectations in the Development of Secondary Pinprick Hypersensitivity: Behavioral-Neurophysiological Evidence and the Role of Pain-Related Fear

Mechanical hypersensitivity, a common symptom of neuropathic pain, reflects increased responsiveness of nociceptive pathways and can be induced temporarily in healthy volunteers using high-frequency electrical stimulation (HFS) of the skin. Expectations modulate acute pain perception and fear of pain has been shown to attenuate and amplify the placebo and nocebo effects respectively. However, the role of expectations and fear in the development of mechanical hypersensitivity remains unclear. The modulatory role of fear and expectations in the development of mechanical hypersensitivity remains so far mainly correlational. Here, we randomly assigned healthy participants (women) to a placebo, nocebo, or control group. In the experimental groups, participants’ expectations of HFS pain were manipulated using verbal suggestions accompanied by an inert treatment. Fear of pain was evaluated both in terms fear of HFS pain and via questionnaires. Sensitivity to mechanical stimulation was assessed by self-reported pinprick ratings before and after HFS; pinprick-evoked potentials (PEPs) elicited by the stimulation were recorded. The placebo group developed the least mechanical hypersensitivity (smaller proximal-distal spread) while the nocebo group developed the most, but only when outliers were excluded. Continuous ratings of expected HFS intensity and unpleasantness predicted the development of mechanical hypersensitivity. Anticipatory pain-related fear only mediated the relationship between HFS unpleasantness expectations and perceived pinprick unpleasantness. Dispositional fear of pain moderated the relationship between expectations and the perceived intensity and unpleasantness of pinpricks. No group differences were observed in PEPs. We provide preliminary evidence that both expectations and fear impact the development of mechanical hypersensitivity

Preprocessing choices do not affect the chances of observing increased scalp recorded gamma-band oscillations in the context of mechanical hypersensitivity.

A recent publication by Gousset et al. (2023) in Clinical Neurophysiology, investigated if experimentally-induced mechanical pinprick hypersensitivity, elicited by applying high-frequency electrical stimulation onto the skin (HFS), is associated with increases pinprick-induced scalp-recorded EEG gamma-band oscillations (GBOs). They found this not to be the case. However, one could argue that some choices made in the preprocessing steps might have affected the results, resulting in a type II error. In this correspondence we report the results of our investigation on whether different choices in preprocessing steps change the results and conclusions presented by Gousset et al

The effect of placebo vs nocebo interventions on the development of secondary hypersensitivity: A pinprick-evoked potentials study

In the present study, we will use a between-subjects design in which participants will be randomized into three groups: a control group, a placebo group and a nocebo group. In each group participants will be told that the aim of the study is to examine the effect of a food supplement on the perception of pain. In each group, we will induce hypersensitivity to mechanical pinpricks using high frequency electrical stimulation (HFS). Before HFS, participants in the experimental groups will receive a capsule containing lactose and they will be told that it will amplify (nocebo group) versus reduce (placebo group) their pain perception during HFS. Next, participants will rate their pain expectancy and pain-related fear, followed by a recording of their skin conductance level as a proxy of pain-related fear. Hypersensitivity will be assessed by measuring the perceived intensity and unpleasantness of mechanical pinpricks before and 20 minutes after HFS

The impact of the social context on the development of secondary hyperalgesia:an experimental study

Social support has been shown to reduce pain ratings and physiological responses to acute pain stimuli. Furthermore, this relationship is moderated by adult attachment styles. However, these effects have not been characterized in experimentally induced symptoms of chronic pain, such as secondary hyperalgesia (SH) which is characterized by an increased sensitivity of the skin surrounding an injury. We aimed to examine whether social support by handholding from a romantic partner can attenuate the development of experimentally induced SH. Thirty-seven women, along with their partners, participated in 2 experimental sessions 1 week apart. In both sessions, SH was induced using an electrical stimulation protocol. In the support condition, the partner was seated across from the participant holding the participant's hand during the electrical stimulation, whereas in the alone condition, the participant went through the stimulation alone. Heart rate variability was measured for both the participant as well as the partner before, during, and after the stimulation. We found that the width of the area of hyperalgesia was significantly smaller in the support condition. Attachment styles did not moderate this effect of social support on the area width. Increasing attachment avoidance was associated with both a smaller width of hyperalgesia and a smaller increase in the sensitivity on the stimulated arm. For the first time, we show that social support can attenuate the development of secondary hyperalgesia and that attachment avoidance may be associated with an attenuated development of secondary hyperalgesia