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

The effect of online social support on experimental pain

Ample evidence shows that in-person social support can alleviate both acute and chronic pain complaints. However, less is known about the effectiveness of online social support. Disparities in availability of and access to in-person social support could make online social support a promising and cost-effective alternative. To this end we aimed to compare the effects of online versus in-person social support on pain induced with a cold-pressor task (CPT). Specifically, 62 pain-free female participants immersed their feet in cold water (1) alone, (2) in the physical presence of a supportive other, (3) while chatting with the supportive other online, and (4) while chatting online with a stranger, in a randomized order. We assessed self-reported pain intensity, pain unpleasantness, and threat value of pain, as well as pain tolerance (i.e. immersion time) and heart rate. Overall, pain intensity and unpleasantness ratings were higher in the alone condition compared to the other conditions. A similar pattern was found in pain tolerance, but the differences were not statistically significant. Heart rate increased during the CPT but was highest in the in-person support condition. Moreover, recovery after cold water immersion was slower in the alone condition compared to the other conditions. In sum, interaction with a supportive other or a stranger, be it online or in-person, led to a reduction in acute pain compared to being alone. This study presents initial evidence that online interaction with others might be an effective alternative to in-person social support in order to reduce acute pain in women. PERSPECTIVE: Online and in-person social support were equally effective in reducing acute experimental cold-pressor pain compared to being alone. There was no difference between social support from strangers or a supportive other.

Distress is positively associated with induced secondary hyperalgesia in people with suppressed HIV

Pain and distress are frequently reported by people with HIV. Although pain is widely acknowledged to contribute to distress, distress may also contribute to pain and its persistence. Given the evidence supporting a relationship between distress and clinical pain, the current study investigated the relationships between distress, secondary hyperalgesia (SH), and persistent pain in people with HIV, reporting pain (n=19) or being pain free (n=26). We anticipated that SH is an important link between distress and persistent pain, with distress potentially exacerbating pain by increasing the responsiveness of neurons in the central nervous system to nociceptive signalling. Our primary hypothesis was that self-reported distress would be positively associated with the induced surface area (primary measure) and magnitude (secondary measure) of SH. The secondary hypothesis was that individuals with persistent pain would display greater induced SH compared to those who reported being pain-free. The results showed that distress was positively associated with the surface area (p=0.02) and the magnitude (p=0.01) of induced SH. However, participants with persistent pain showed no difference in the surface area of SH compared to pain-free participants (p=0.87), and those with pain displayed a marginally lower magnitude of SH (p=0.05). These findings suggest that distress may be a worthy target of interventions in people exposed to acutely painful events. While this relationship may not be specific to people with HIV, further research is needed to establish its relevance to people without HIV.

Experimentally induced central sensitization is accompanied by alterations in electroencephalographical microstate parameters

ABSTRACT

Pain perception is a dynamic and time-varying phenomenon. The high temporal resolution of electroencephalography (EEG) can be leveraged to gain insight into its cortical dynamics. Electroencephalography microstate analysis is a novel technique that parses multichannel EEG signals into a limited number of quasi-stable topographies (microstates) that have a meaningful temporal structure and have been linked to the activity of resting state networks. In recent years, several studies have investigated alterations in EEG microstate parameters associated with acute and chronic pain states, with mixed results. In the present study, we used high-frequency stimulation (HFS), in healthy human volunteers, to induce mechanical hypersensitivity (a perceptual correlate of central sensitization) and investigated (1) changes in microstate parameters before vs after the induction of mechanical hypersensitivity and (2) whether microstate parameters before HFS were linked to the development of mechanical hypersensitivity. Results showed that the duration of microstate E, typically related to the activity of the salience/default mode network, was consistently decreased post-HFS. The global explained variance of microstates A (Auditory network) and E and coverage of microstate A were positively associated with mechanical hypersensitivity. Conversely, the transition probabilities from microstates B (Visual network) to A and the bidirectional transition probabilities between B and C (saliency and default mode networks) were negatively associated with mechanical hypersensitivity. We discuss these findings in the context of the functional significance of EEG microstates. Our results highlight the potential utility of microstate analysis in understanding pain processing and its potential link to changes in the nociceptive system.

Verbal Support From a Stranger Reduces the Development of Mechanical Hypersensitivity: Behavioral and Neurophysiological Evidence

Hand-holding reduces experimentally induced acute pain and buffers against the development of mechanical secondary hypersensitivity, an indirect proxy of central sensitization. Here, we tested if verbal support from a stranger, a common occurrence in clinical contexts, exerts the same effects. In this preregistered study, 44 healthy female participants were assigned to an alone or support group whereby a supportive female stranger encouraged them through the painful procedure leading to secondary mechanical hypersensitivity. Mechanical hypersensitivity was measured via self-reports and by the size of the anteroposterior and mediolateral spread of mechanical hypersensitivity. We investigated the moderating role of attachment style on self-reports and the effects of support on skin conductance level, salivary cortisol, and pinprick-evoked potentials. We also tested whether theta/beta ratio in the resting-state electroencephalogram predicted mechanical hypersensitivity. Self-reported ratings and the late part of the pinprick-evoked potentials were reduced in the support group, but the spread of mechanical hypersensitivity was not. Attachment anxiety and avoidance moderated the self-reported intensity such that individuals with higher attachment anxiety and avoidance scores reported lower intensity ratings in the support group. No significant effect of the verbal support was observed on skin conductance level and salivary cortisol. The theta/beta ratio did not predict the extent of hypersensitivity. Our data indicate that, in women, verbal support during intense pain leading to hypersensitivity is effective on some behavioral outcomes, but altogether the lack of group differences in cortisol, self-reported stress, and skin conductance does not provide strong support for the stress-buffering hypothesis. PERSPECTIVE: Verbal support by a stranger during a painful procedure leading to secondary mechanical hypersensitivity attenuated the development of some measures of mechanical hypersensitivity and associated neural responses in healthy female participants. No evidence was found for the role of stress. DATA AVAILABILITY: The authors will make all data available upon request.

Top-down attention does not modulate mechanical hypersensitivity consecutive to central sensitization: insights from an experimental analysis

ABSTRACT

According to the neurocognitive model of attention to pain, when the attentional resources invested in a task unrelated to pain are high, limited cognitive resources can be directed toward the pain. This is supported by experimental studies showing that diverting people's attention away from acute pain leads to experiencing less pain. Theoretical work has suggested that this phenomenon may present a top-down modulatory mechanism for persistent pain as well. However, conclusive empirical evidence is lacking. To fill this gap, we used a preregistered, double-blind, between-subject study design to investigate whether performing a tailored, demanding, and engaging working memory task unrelated to pain (difficult) vs a task that requires less mental effort to be performed (easy), could lead to lower development of secondary hypersensitivity-a hallmark of central sensitization. Eighty-five healthy volunteers, randomly assigned to one of the 2 conditions, performed a visual task with a different cognitive load (difficult vs easy), while secondary hypersensitivity was induced on their nondominant forearm using high-frequency stimulation. To assess the development of secondary hypersensitivity, sensitivity to mechanical stimuli was measured 3 times: T0, for baseline and 20 (T1) and 40 (T2) minutes after the procedure. We did not observe any significant difference in the development of secondary hypersensitivity between the 2 groups, neither in terms of the intensity of mechanical sensitivity nor its spatial extent. Our results suggest that a top-down modulation through attention might not be sufficient to affect pain sensitization and the development of secondary hypersensitivity.

The prevalence of depression in women with pregnancy-related pelvic girdle pain: A systematic review and meta-analysis

Background and Aims

Pregnancy-related pelvic girdle pain (PPGP) is estimated to affect between 20% and 70% of pregnant women with 10% experiencing it for more than 3 months postpartum. Women may also experience depression during this period. Understanding the prevalence of depression in women with PPGP is important to inform clinical management. This systematic review aimed to examine the prevalence of depression in women with PPGP in the antepartum and postpartum periods.

Methods

A systematic review and meta-analysis. Seven databases were searched from inception until May 24, 2023, combining keywords relating to pelvic girdle pain (PGP), depression, and pregnancy. Two investigators independently screened study titles and abstracts against the eligibility criteria, extracting data characteristics of all included studies. Included articles were assessed for risk of bias. Summary estimates of the prevalence of depression were calculated with a random effects meta-analysis (stratified by antepartum and postpartum periods).

Results

Eleven studies (3172 participants) were included with nine suitable for meta-analysis. The overall summary estimate of prevalence of depression among women with PPGP was 24% (95% confidence interval [CI] = 15%-37%), with significant heterogeneity between studies (I 2 = 97%, p < 0.01). Among individual studies, the estimates ranged from 18% to 48% in the antepartum PGP population and from 5% to 39% in the postpartum PGP population. The summary estimate in the antepartum group was 37% (95% CI = 19%-59%; prediction interval 8%-81%) and 15% (95% CI = 7%-30%; prediction interval 3%-56%) in the postpartum group, although time (antepartum vs. postpartum) did not have a statistically significant moderating effect (p = 0.06). Two thirds of the studies were undertaken with Scandinavian populations, limiting the generalizability of these findings.

Conclusion

Summary estimates for the prevalence of depression in women with PPGP are similar to previous studies investigating depression in the general peri-natal population.