The molecular neurobiology of chronic pain-induced depression

Electro-acupuncture inhibits HDAC2 via modulating gut microbiota to ameliorate SNI-induced pain and depression-like behavior in rats

BACKGROUND

Depression and chronic pain frequent co-occur, exacerbating each other's symptoms and hindering treatment. Emerging studies have highlighted abnormal gut microbiota in both conditions. Previous studies have demonstrated the clinical effectiveness of electro-acupuncture (EA) in managing these conditions, yet the underlying mechanisms remain elusive.

METHODS

Spared nerve injury (SNI) was employed to induce chronic pain and depression-like behavior. Rats were randomly assigned to sham SNI (SS), SNI, and EA groups. SNI surgery was performed on all rats, except those in SS group, which underwent sham SNI surgery. Then EA group received 5 weeks of EA treatment. Pain and depression-like behavior were assessed through paw withdrawal threshold, sucrose-preference test, and forced swim test. Gut microbiota composition was analyzed via 16S rDNA sequencing. Brain-Derived Neurotrophic Factor (BDNF) and acetylation-related proteins in the medial prefrontal cortex (mPFC) were evaluated through enzyme-linked immunosorbent assay and western blot.

RESULTS

EA treatment significantly ameliorated pain and depression-like behavior. The 16S rDNA sequencing showed EA modulated gut microbiota composition, increased short-chain fatty acids (SCFAs)-producing bacteria, including Akkermansi, Ruminococcaceae and Lachnospiraceae family, particularly Akkermansia. Furthermore, EA increased BDNF, AcH3 and decreased HDAC2 in mPFC. Notably, SCFAs-producing bacteria exhibited a negative correlation with HDAC2 levels.

LIMITATIONS

This study exclusively investigated microbiota differences resulting from EA stimulation, without delving into the functional variations brought about by these microbial distinctions.

CONCLUSIONS

The therapeutic effects of EA on the comorbidity of chronic pain and depression may involve the modulation of the gut microbiota, resulting in histone acetylation changes and upregulation of BDNF.

Bio-Inspired Carbon Dots as Malondialdehyde Indicator for Real-Time Visualization of Lipid Peroxidation in Depression

Brain lipidic peroxidation is closely associated with the pathophysiology of various psychiatric diseases including depression. Malondialdehyde (MDA), a reactive aldehyde produced in lipid region, serves as a crucial biomarker for lipid peroxidation. However, techniques enabling real-time detection of MDA are still lacking due to the inherent trade-off between recognition dynamics and robustness. Inspired by the structure of phospholipid bilayers, amphiphilic carbon dots named as CG-CDs targeted to cell membrane are designed for real-time monitoring of MDA fluctuations. The design principle relies on the synergy of dynamic hydrogen bonding recognition and cell membrane targetability. The latter facilitates the insertion of CG-CDs into lipid regions and provides a hydrophobic environment to stabilize the labile hydrogen bonding between CG-CDs and MDA. As a result, recognition robustness and dynamics are simultaneously achieved for CG-CDs/MDA, allowing for in situ visualization of MDA kinetics in cell membrane due to the instant response (<5 s), high sensitivity (9-fold fluorescence enhancement), intrinsic reversibility (fluorescence on/off), and superior selectivity. Subsequently, CG-CDs are explored to visualize nerve cell membrane impairment in depression models of living cells and zebrafish, unveiling the extensive heterogeneity of the lipid peroxidation process and indicating a positive correlation between MDA levels and depression.

The effect and mechanism of low-dose esketamine in neuropathic pain-related depression-like behavior in rats

BACKGROUND

Clinical evidence suggests that Esketamine (ESK) is an effective treatment for depression. However, the effects of Esketamine in treating depression-like behavior induced by neuropathic pain is unclear. The underlying molecular mechanisms require further investigation to provide new therapeutic targets for the treatment of clinical neuropathic pain-related depression.

METHODS

A neuropathic pain-related depression model was established in rats with spared nerve injury (SNI). Male Sprague-Dawley rats were randomly divided into four groups: Sham Group, SNI group, SNI + Normal Saline (NS) Group and SNI + ESK5mg/kg Group. Mechanical pain thresholds were measured to assess pain sensitivity in SNI rats. On the 14th day after surgery a forced swim test and sucrose preference test were used to evaluate the depressive-like behavior of rats in each group. Further, a proteomic analysis was used to quantify differentially expressed proteins. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were analyzed to explore the main protein targets of SNI in the medial prefrontal cortex. The expression of proteins was detected by Western blotting.

RESULTS

A neuropathic pain-related depression model was established. Compared with the Sham group, the mechanical pain threshold was decreased significantly (13.2 ± 1.0 vs. 0.7 ± 0.01 g n = 8), while immobility on the forced swim test was also decreased (93.1 ± 7.4 vs. 169.5 ± 9.6 s n = 8), and sucrose preference rate was significantly increased (98.8 ± 0.3 vs. 73.1 ± 1.4n = 7) in SNI group rats. Compared with the SNI + NS group, the mechanical pain threshold was not statistically significant, while immobility on the forced swim test was clearly decreased (161.1 ± 11.6 vs. 77.9 ± 5.0 s n = 8), and sucrose preference rate was significantly increased (53.1 ± 8.9 vs. 96.1 ± 1.4n = 7) in SNI + ESK5mg/kg group rats. To further investigate the underlying mechanism, we employed proteomics to identify proteins exhibiting more than a 1.2-fold difference (P < 0.05) in expression levels within each group for subsequent analysis. Relative to the Sham group, 88 downregulated and 104 up-regulated proteins were identified in the SNI group, while 120 and 84 proteins were up- and down-regulated in the Esketamine treatment group compared with the SNI + NS group. Compared with Sham group, the expressions of mGluR5 and Homer1a were up-regulated in the medial prefrontal cortex (mPFC) in SNI group (mGluR5:0.97 ± 0.05 vs 1.47 ± 0.15, Homer1a:1.03 ± 0.06 vs 1.46 ± 0.16n = 6), and down-regulated after intervention with Esketamine (mGluR5:1.54 ± 0.11 vs 1.06 ± 0.07, Homer1a:1.51 ± 0.13 vs 1.12 ± 0.34n = 6).

CONCLUSIONS

Low-dose Esketamine appeared to relieve depression-like behavior induced by neuropathic pain. The Homer1a-mGluR5 signaling pathway might be the mechanism of antidepressant effect of Esketamine.

Bidirectional relationship between chronic pain and depressive symptoms in middle-aged and older adults

OBJECTIVE

To assess the bidirectional association between chronic pain and depressive symptoms among middle-aged and older adults from two prospective cohort studies.

METHODS

We used prospective data (12y of follow-up) from the English Longitudinal Study of Ageing (n = 9149, 5018 women, 65.0 ± 10.2y) and the Health and Retirement Study (n = 16,883, 9810 women, 66.9 ± 10.3y), including data from seven waves of each cohort between 2006 and 2018/2019. Depressive symptoms were assessed using the Centre of Epidemiological Studies Depression scale, while chronic pain was estimated using questions about the frequency of being troubled with pain. We used random-intercept cross-lagged panel models to assess the bidirectional association between pain and depressive symptoms, adjusting for potential confounders.

RESULTS

There was a cross-lagged effect of chronic pain on depressive symptoms (ELSA: β: 0.038; 95%CI: 0.011-0.066. Standardized coefficient (B): 0.021.

SHARE

β: 0.044; 95%CI: 0.023-0.065. B: 0.023-0.024) as well as depressive symptoms on pain (ELSA: β: 0.010; 95%CI: 0.002-0.018. B: 0.017-0.019.

SHARE

0.011; 95%CI: 0.005-0.017. B: 0.020-0.021). Moreover, there were auto-regressive effects of both chronic pain (ELSA: β: 0.149; 95%CI: 0.128-0.171.

SHARE

β: 0.129; 95%CI: 0.112-0.145) and depressive symptoms (ELSA: β: 0.149; 95%CI: 0.130-0.168.

SHARE

β: 0.169; 95%CI: 0.154-0.184).

CONCLUSION

We identified a modest bidirectional association between depressive symptoms and chronic pain, using two large prospective ageing cohorts.

Substance P's Impact on Chronic Pain and Psychiatric Conditions-A Narrative Review

Substance P (SP) plays a crucial role in pain modulation, with significant implications for major depressive disorder (MDD), anxiety disorders, and post-traumatic stress disorder (PTSD). Elevated SP levels are linked to heightened pain sensitivity and various psychiatric conditions, spurring interest in potential therapeutic interventions. In chronic pain, commonly associated with MDD and anxiety disorders, SP emerges as a key mediator in pain and emotional regulation. This review examines SP's impact on pain perception and its contributions to MDD, anxiety disorders, and PTSD. The association of SP with increased pain sensitivity and chronic pain conditions underscores its importance in pain modulation. Additionally, SP influences the pathophysiology of MDD, anxiety disorders, and PTSD, highlighting its potential as a therapeutic target. Understanding SP's diverse effects provides valuable insights into the mechanisms underlying these psychiatric disorders and their treatment. Further research is essential to explore SP modulation in psychiatric disorders and develop more effective treatment strategies.

The effects of osteopathic manipulative treatment on pain and disability in patients with chronic low back pain: a single-blinded randomized controlled trial

CONTEXT

The evidence for the efficacy of osteopathic manipulative treatment (OMT) in the management of low back pain (LBP) is considered weak by systematic reviews, because it is generally based on low-quality studies. Consequently, there is a need for more randomized controlled trials (RCTs) with a low risk of bias.

OBJECTIVES

The objective of this study is to evaluate the efficacy of an OMT intervention for reducing pain and disability in patients with chronic LBP.

METHODS

A single-blinded, crossover, RCT was conducted at a university-based health system. Participants were adults, 21-65 years old, with nonspecific LBP. Eligible participants (n=80) were randomized to two trial arms: an immediate OMT intervention group and a delayed OMT (waiting period) group. The intervention consisted of three to four OMT sessions over 4-6 weeks, after which the participants switched (crossed-over) groups. The primary clinical outcomes were average pain, current pain, Patient-Reported Outcomes Measurement Information System (PROMIS) 29 v1.0 pain interference and physical function, and modified Oswestry Disability Index (ODI). Secondary outcomes included the remaining PROMIS health domains and the Fear Avoidance Beliefs Questionnaire (FABQ). These measures were taken at baseline (T0), after one OMT session (T1), at the crossover point (T2), and at the end of the trial (T3). Due to the carryover effects of OMT intervention, only the outcomes obtained prior to T2 were evaluated utilizing mixed-effects models and after adjusting for baseline values.

RESULTS

Totals of 35 and 36 participants with chronic LBP were available for the analysis at T1 in the immediate OMT and waiting period groups, respectively, whereas 31 and 33 participants were available for the analysis at T2 in the immediate OMT and waiting period groups, respectively. After one session of OMT (T1), the analysis showed a significant reduction in the secondary outcomes of sleep disturbance and anxiety compared to the waiting period group. Following the entire intervention period (T2), the immediate OMT group demonstrated a significantly better average pain outcome. The effect size was a 0.8 standard deviation (SD), rendering the reduction in pain clinically significant. Further, the improvement in anxiety remained statistically significant. No study-related serious adverse events (AEs) were reported.

CONCLUSIONS

OMT intervention is safe and effective in reducing pain along with improving sleep and anxiety profiles in patients with chronic LBP.

Structural and functional abnormalities in the medial prefrontal cortex were associated with pain and depressive symptoms in patients with adhesive capsulitis

Introduction

Chronic pain and depression have been shown to coexist in patients with adhesive capsulitis (AC). Recent studies identified the shared brain plasticity between pain and depression; however, how such neuroplasticity contributes to AC remains unclear. Here, we employed a combination of psychophysics, structural MRI, and functional MRI techniques to examine the brain's structural and functional changes in AC.

Methods

Fifty-two patients with AC and 52 healthy controls (HCs) were included in our study. Voxelwise comparisons were performed to reveal the differences in grey matter volume (GMV) and regional homogeneity (ReHo) between AC and HCs. Furthermore, region of interest to whole brain functional connectivity (FC) was calculated and compared between the groups. Finally, Pearson correlation coefficients were computed to reveal the association between clinical data and brain alterations. Mediation analyses were performed to investigate the path association among brain alterations and clinical measures.

Results

Three main findings were observed: (1) patients with AC exhibited a higher depression subscale of hospital anxiety and depression scale (HADS-D) score correlating with the GMV within the right medial prefrontal cortices (mPFC) compared with HCs; (2) relative to HCs, patients with AC exhibited lower ReHo within the right mPFC, which largely overlapped with the structural abnormalities; (3) the impact of pain duration on HADS-D score was mediated by ventral part of medial prefrontal cortices (vmPFC) GMV in patients with AC.

Conclusion

In summary, our current findings suggest that vmPFC alterations correlate with both the pain duration and the emotional comorbidities experienced by patients with AC. Our research provides an enhanced comprehension of the underlying mechanisms of AC, thereby facilitating the development of more effective treatment approaches for AC.

Postpartum pain and the risk of postpartum depression: A meta-analysis of observational studies

OBJECTIVE

This meta-analysis of observational studies aimed to derive a more precise estimation of the relationship between postpartum pain and postpartum depression (PPD).

METHODS

A systematic literature search was completed in the following databases from inception to September 26, 2022: PubMed, Embase, and Web of Science. Quality evaluation of each study was achieved through Newcastle-Ottawa scale (NOS) assessment. Heterogeneity across studies was evaluated by Cochran's Q test and I2 test. Pooled estimates of odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were analyzed using fixed-effects model or random-effects model, according to heterogeneity. Subgroup analysis, sensitivity analysis, and Egger's test were also performed.

RESULTS

From the identified 1884 articles, a total of 8 studies involving 3973 participants were included in the final meta-analysis. Seven of the 8 studies were evaluated as high-quality, with NOS scores ≥7. A significant heterogeneity was observed (I2  = 66.5%, p = 0.004) among eight studies. Therefore, the performed random-effect model suggested a significant association between postpartum pain and PPD risk (OR 1.29, 95% CI 1.10-1.52, p = 0.002). However, the subgroup analyses did not define the source of heterogeneity. Moreover, the sensitivity analysis showed the stability of the pooled results, but the significant publication bias was identified (p = 0.009). The trim and fill method was performed and resulted in an OR of 1.14 (95% CI 0.95-1.37, p = 0.162).

CONCLUSIONS

This meta-analysis found a potential association between postpartum pain and PPD. Further researches are needed to provide more robust evidences.

Pharmacological and Non-pharmacological Approaches for the Management of Neuropathic Pain in Multiple Sclerosis

Multiple sclerosis is a chronic inflammatory disease that affects the central nervous system and can cause various types of pain including ongoing extremity pain, Lhermitte's phenomenon, trigeminal neuralgia, and mixed pain. Neuropathic pain is a major concern for individuals with multiple sclerosis as it is directly linked to myelin damage in the central nervous system and the management of neuropathic pain in multiple sclerosis is challenging as the options available have limited efficacy and can cause unpleasant side effects. The literature search was conducted across two databases, PubMed, and Google Scholar. Eligible studies included clinical trials, observational studies, meta-analyses, systematic reviews, and narrative reviews. The objective of this article is to provide an overview of literature on pharmacological and non-pharmacological strategies employed in the management of neuropathic pain in multiple sclerosis. Pharmacological options include cannabinoids, muscle relaxants (tizanidine, baclofen, dantrolene), anticonvulsants (benzodiazepines, gabapentin, phenytoin, carbamazepine, lamotrigine), antidepressants (duloxetine, venlafaxine, tricyclic antidepressants), opioids (naltrexone), and botulinum toxin variants, which have evidence from various clinical trials. Non-pharmacological approaches for trigeminal neuralgia may include neurosurgical methods. Non-invasive methods, physical therapy, and psychotherapy (cognitive behavioral therapy, acceptance and commitment therapy and mindfulness-based stress reduction) may be recommended for patients with neuropathic pain in multiple sclerosis. The choice of treatment depends on the severity and type of pain as well as other factors, such as patient preferences and comorbidities. There is a pressing need for healthcare professionals and researchers to prioritize the development of better strategies for managing multiple sclerosis-induced neuropathic pain.

Chronic pain predicts a worse response to depression treatment, regardless of thyroid function or psychotropics prescribed

BACKGROUND

Chronic pain (CP) and thyroid hormones' (TH) abnormalities are associated with depression, but the impact of pain and TH fluctuation on the response to depression treatment is uncertain.

METHODS

Eighty-eight patients with major depression were evaluated before and after 6 months of specific treatment, through scales of symptoms' severity (HAM-D-17), psychomotor disturbance (CORE), and quality of life (WHOQOL-Bref). We reviewed psychiatric medications and measured TSH, T3 and T4. We used Generalized Estimating Equations to assess the interaction effect between CP and treatment time on depression severity and TH levels, and Bonferroni to compare means.

RESULTS

47.7 % of the patients had CP. Patients with and without CP did not differ at baseline. At follow-up, those with CP experienced a more modest decrease in symptoms' severity and no improvement in any domain of psychomotor disturbance, contrasting with a decrease of over 40 % from the baseline values of CORE in patients without CP (non-CP). Initial and final scores were respectively: HAM-D CP 24.06 and 19.3, Δ = -4.75; HAM-D non-CP 22.92 and 14.7, Δ = -8.21; CORE CP 5.36 and 5.24, Δ = -0.12; CORE non-CP 5.8 and 3.22, Δ = -2.57. There was no interaction with TH or life quality. Model adjustments for psychotropic drugs received and sensitivity analysis excluding somatic symptoms from severity scales did not impact the results.

LIMITATIONS

Findings may not replicate in mildly depressed patients from primary care. Pain scales were not applied.

CONCLUSIONS

Individuals with chronic pain showed a suboptimal response to depression treatment, regardless of the medications used or TH levels.

A Deep-Learning Driven Investigation of the Circuit Basis for Reflexive Hypersensitivity to Thermal Pain

Objectively measuring animal behavior is vital to understanding the neural circuits underlying pain. Recent progress in machine vision has presented unprecedented scope in behavioral analysis. Here, we apply DeepLabCut (DLC) to dissect mouse behavior on the thermal-plate test - a commonly used paradigm to ascertain supraspinal contributions to noxious thermal sensation and pain hypersensitivity. We determine the signature characteristics of the pattern of mouse movement and posture in 3D in response to a range of temperatures from innocuous to noxious on the thermal-plate test. Next, we test how acute chemical and chronic inflammatory injuries sensitize mouse behaviors. Repeated exposure to noxious temperatures on the thermal plate can induce learning. In this study, we design a novel assay and formulate an analytical pipeline to facilitate the dissection of plasticity mechanisms in pain circuits in the brain. Last, we record and test how activating Tacr1 expressing PBN neurons (PBNTacr1) - a population responsive to sustained noxious stimuli- affects mouse behavior on the thermal plate test. Taken together, we demonstrate that by tracking a single body part of a mouse, we can reveal the behavioral signatures of mice exposed to noxious surface temperatures, report the alterations of the same when injured, and determine if a molecularly and anatomically defined pain-responsive circuit plays a role in the reflexive hypersensitivity to thermal pain.

The Inhibition of Neuropathic Pain Incited by Nerve Injury and Accompanying Mood Disorders by New Heme Oxygenase-1 Inducers: Mechanisms Implicated

Neuropathic pain is a type of pain that persists for a long time and becomes pathological. Additionally, the anxiodepressive disorders derived from neuropathic pain are difficult to palliate with the current treatments and need to be resolved. Then, using male mice with neuropathic pain provoked by chronic constriction of the sciatic nerve (CCI), we analyzed and compared the analgesic actions produced by three new heme oxygenase 1 (HO-1) inducers, 1m, 1b, and 1a, with those performed by dimethyl fumarate (DMF). Their impact on the anxiety- and depressive-like comportments and the expression of the inflammasome NLRP3, Nrf2, and some antioxidant enzymes in the dorsal root ganglia (DRG) and amygdala (AMG) were also investigated. Results revealed that the administration of 1m, 1b, and DMF given orally for four days inhibited the allodynia and hyperalgesia caused by CCI, while 1a merely reduced the mechanical allodynia. However, in the first two days of treatment, the antiallodynic effects produced by 1m were higher than those of 1a and DMF, and its antihyperalgesic actions were greater than those produced by 1b, 1a, and DMF, revealing that 1m was the most effective compound. At four days of treatment, all drugs exerted anxiolytic and antidepressant effects, decreased the NLRP3 levels, and increased/normalized the Nrf2, HO-1, and superoxide dismutase 1 levels in DRG and AMG. Data indicated that the dual modulation of the antioxidant and inflammatory pathways produced by these compounds, especially 1m, is a new promising therapeutic approach for neuropathic pain and related emotional illnesses.

Resilience to Pain-Related Depression in σ1 Receptor Knockout Mice Is Associated with the Reversal of Pain-Induced Brain Changes in Affect-Related Genes

Mice lacking the σ1 receptor chaperone (σ1R-/-) are resilient to depressive-like behaviors secondary to neuropathic pain. Examining the resilience's brain mechanisms could help develop conceptually novel therapeutic strategies. We explored the diminished motivation for a natural reinforcer (white chocolate) in the partial sciatic nerve ligation (PSNL) model in wild-type (WT) and σ1R-/- mice. In the same mice, we performed a comprehensive reverse transcription quantitative PCR (qPCR) analysis across ten brain regions of seven genes implicated in pain regulation and associated affective disorders, such as anxiety and depression. PSNL induced anhedonic-like behavior in WT but not in σ1R-/- mice. In WT mice, PSNL up-regulated dopamine transporter (DAT) and its rate-limiting enzyme, tyrosine hydroxylase (Th), in the ventral tegmental area (VTA) and periaqueductal gray (PAG) as well as the serotonin transporters (SERT) and its rate-limiting enzyme tryptophan hydroxylase 2 (Tph2) in VTA. In addition, μ-opioid receptor (MOR) and σ1R were up-regulated in PAG, and MOR was also elevated in the somatosensory cortex (SS) but down-regulated in the striatum (STR). Finally, increased BDNF was found in the medial prefrontal cortex (mPFC) and hypothalamus (HPT). Sham surgery also produced PSNL-like expression changes in VTA, HPT, and STR. Genetic deletion of the σ1R in mice submitted to PSNL or sham surgery prevented changes in the expression of most of these genes. σ1R is critically involved in the supraspinal gene expression changes produced by PSNL and sham surgery. The changes in gene expression observed in WT mice may be related to pain-related depression, and the absence of these changes observed in σ1R-/- mice may be related to resilience.

Converging circuits between pain and depression: the ventral tegmental area as a therapeutic hub

Chronic pain and depression are highly prevalent pathologies and cause a major socioeconomic burden to society. Chronic pain affects the emotional state of the individuals suffering from it, while depression worsens the prognosis of chronic pain patients and may diminish the effectiveness of pain treatments. There is a high comorbidity rate between both pathologies, which might share overlapping mechanisms. This review explores the evidence pinpointing a role for the ventral tegmental area (VTA) as a hub where both pain and emotional processing might converge. In addition, the feasibility of using the VTA as a possible therapeutic target is discussed. The role of the VTA, and the dopaminergic system in general, is highly studied in mood disorders, especially in deficits in reward-processing and motivation. Conversely, the VTA is less regarded where it concerns the study of central mechanisms of pain and its mood-associated consequences. Here, we first outline the brain circuits involving central processing of pain and mood disorders, focusing on the often-understudied role of the dopaminergic system and the VTA. Next, we highlight the state-of-the-art findings supporting the emergence of the VTA as a link where both pathways converge. Thus, we envision a promising part for the VTA as a putative target for innovative therapeutic approaches to treat chronic pain and its effects on mood. Finally, we emphasize the urge to develop and use animal models where both pain and depression-like symptoms are considered in conjunction.

Janus effect of the anterior cingulate cortex: Pain and emotion

Over the past 20 years, clinical and preclinical studies point to the anterior cingulate cortex (ACC) as a site of interest for several neurological and psychiatric conditions. The ACC plays a critical role in emotion, autonomic regulation, pain processing, attention, memory and decision making. An increasing number of studies have demonstrated the involvement of the ACC in the emotional component of pain and its comorbidity with emotional disorders such as anxiety and depression. Thanks to the development of animal models combined with state-of-the-art technologies, we now have a better mechanistic understanding of the functions of the ACC. Hence, the primary aim of this review is to compile the most recent preclinical studies on the role of ACC in the emotional component and consequences of chronic pain. Herein, we thus thoroughly describe the pain-induced electrophysiological, molecular and anatomical alterations in the ACC and in its related circuits. Finally, we discuss the next steps that are needed to strengthen our understanding of the involvement of the ACC in emotional and pain processing.

Brain-predicted age difference mediates the association between PROMIS sleep impairment, and self-reported pain measure in persons with knee pain

Knee pain, the most common cause of musculoskeletal pain (MSK), constitutes a severe public health burden. Its neurobiological causes, however, remain poorly understood. Among many possible causes, it has been proposed that sleep problems could lead to an increase in chronic pain symptomatology, which may be driven by central nervous system changes. In fact, we previously found that brain cortical thickness mediated the relationship between sleep qualities and pain severity in older adults with MSK. We also demonstrated a significant difference in a machine-learning-derived brain-aging biomarker between participants with low-and high-impact knee pain. Considering this, we examined whether brain aging was associated with self-reported sleep and pain measures, and whether brain aging mediated the relationship between sleep problems and knee pain. Exploratory Spearman and Pearson partial correlations, controlling for age, sex, race and study site, showed a significant association of brain aging with sleep related impairment and self-reported pain measures. Moreover, mediation analysis showed that brain aging significantly mediated the effect of sleep related impairment on clinical pain and physical symptoms. Our findings extend our prior work demonstrating advanced brain aging among individuals with chronic pain and the mediating role of brain-aging on the association between sleep and pain severity. Future longitudinal studies are needed to further understand whether the brain can be a therapeutic target to reverse the possible effect of sleep problems on chronic pain.

Exploring the bidirectional relationship between pain and mental disorders: a comprehensive Mendelian randomization study

BACKGROUND

The close relationship between pain and mental health problems is well-known, and psychological intervention can provide an effective alternative to medication-based pain relief. However, previous studies on the connection between pain and psychological problems, the findings thus far have been inconclusive, limiting the potential for translating psychological interventions into clinical practice. To complement the gap, this study utilized genetic data and Mendelian randomization (MR) to examine the potential relationship between pain in different parts and common mental disorders.

METHODS

Based on the instrumental variables selected from the Genome-wide association study summary statistics of localized pain and mental disorders, we conducted bidirectional two-sample MR analyses to infer bidirectional causal associations between pain and mental disorders. The inverse-variance weighted MR method and MR-Egger were used as the primary statistical method according to the horizontal pleiotropy and heterogeneity level. We reported the odds ratio to infer the causal effect between pain and mental disorders. F statistic was calculated to measure the statistical efficacy of the analyses.

RESULTS

Insomnia is causally related to the genetic susceptibility of multisite pain including head (OR = 1.09, 95% CI: 1.06-1.12), neck/shoulder (OR = 1.12, 95% CI: 1.07-1.16), back (OR = 1.12, 95% CI: 1.07-1.18) and hip (OR = 1.08, 95% CI: 1.05-1.10). Reversely, headache (OR = 1.14, 95% CI: 1.05-1.24), neck/shoulder pain (OR = 1.95, 95% CI: 1.03-3.68), back pain (OR = 1.40, 95% CI: 1.22-1.60), and hip pain (OR = 2.29, 95% CI: 1.18-4.45) promote the genetic liability of insomnia. Depression is strongly associated with the predisposition of multisite pain including headache (OR = 1.28, 95% CI: 1.08-1.52), neck/shoulder pain (OR = 1.32, 95% CI: 1.16-1.50), back pain (OR = 1.35, 95% CI: 1.10-1.66) and stomach/abdominal pain (OR = 1.14, 95% CI: 1.05-1.25), while headache (OR = 1.06, 95% CI: 1.03-1.08), neck/shoulder (OR = 1.09, 95% CI: 1.01-1.17), back (OR = 1.08, 95% CI: 1.03-1.14), and stomach/abdominal pain (OR = 1.19, 95% CI: 1.11-1.26) are predisposing factors for depression. Additionally, insomnia is associated with the predisposition of facial, stomach/abdominal, and knee pain, anxiety was associated with the predisposition of neck/shoulder and back pain, while the susceptibilities of hip and facial pain are influenced by depression, but these associations were unidirectional.

CONCLUSIONS

Our results enhance the understanding of the complex interplay between pain and mental health and highlight the importance of a holistic approach to pain management that addresses both physical and psychological factors.

Discovery of RC-752, a Novel Sigma-1 Receptor Antagonist with Antinociceptive Activity: A Promising Tool for Fighting Neuropathic Pain

Neuropathic pain (NP) is a chronic condition resulting from damaged pain-signaling pathways. It is a debilitating disorder that affects up to 10% of the world's population. Although opioid analgesics are effective in reducing pain, they present severe risks; so, there is a pressing need for non-opioid pain-relieving drugs. One potential alternative is represented by sigma-1 receptor (S1R) antagonists due to their promising analgesic effects. Here, we report the synthesis and biological evaluation of a series of S1R antagonists based on a 2-aryl-4-aminobutanol scaffold. After assessing affinity toward the S1R and selectivity over the sigma-2 receptor (S2R), we evaluated the agonist/antagonist profile of the compounds by investigating their effects on nerve growth factor-induced neurite outgrowth and aquaporin-mediated water permeability in the presence and absence of oxidative stress. (R/S)-RC-752 emerged as the most interesting compound for S1R affinity (K_i S1R = 6.2 ± 0.9) and functional antagonist activity. Furthermore, it showed no cytotoxic effect in two normal human cell lines or in an in vivo zebrafish model and was stable after incubation in mouse plasma. (R/S)-RC-752 was then evaluated in two animal models of NP: the formalin test and the spinal nerve ligation model. The results clearly demonstrated that compound (R/S)-RC-752 effectively alleviated pain in both animal models, thus providing the proof of concept of its efficacy as an antinociceptive agent.

Role of GABAergic system in the comorbidity of pain and depression

Patients with chronic pain often suffer with depressive symptoms, and these two conditions can be aggravated by each other over time, leading to an increase in symptom intensity and duration. The comorbidity of pain and depression poses a significant challenge to human health and quality of life, as it is often difficult to diagnose early and treat effectively. Therefore, exploring the molecular mechanisms underlying the comorbidity of chronic pain and depression is crucial to identifying new therapeutic targets for treatment. However, understanding the pathogenesis of comorbidity requires examining interactions among multiple factors, which calls for an integrative perspective. While several studies have explored the role of the GABAergic system in pain and depression, fewer have examined its interactions with other systems involved in their comorbidity. Here, we review the evidence that the role of GABAergic system in the comorbidity of chronic pain and depression, as well as the interactions between the GABAergic system and other secondary systems involved in pain and depression comorbidity, providing a comprehensive understanding of their intricate interplay.

Asymmetric activation of microglia in the hippocampus drives anxiodepressive consequences of trigeminal neuralgia in rodents

BACKGROUND AND PURPOSE

Patients suffering from trigeminal neuralgia are often accompanied by anxiety and depression. Microglia-mediated neuroinflammation is involved in the development of neuropathic pain and anxiodepression pathogenesis. Whether and how microglia are involved in trigeminal neuralgia-induced anxiodepression remains unclear.

EXPERIMENTAL APPROACH

Unilateral constriction of the infraorbital nerve (CION) was performed to establish trigeminal neuralgia in rat and mouse models. Mechanical allodynia and anxiodepressive-like behaviours were measured. Optogenetic and pharmacological manipulations were employed to investigate the role of hippocampal microglia in anxiety and depression caused by trigeminal neuralgia.

KEY RESULTS

Trigeminal neuralgia activated ipsilateral but not contralateral hippocampal microglia, up-regulated ipsilateral hippocampal ATP and interleukin-1β (IL-1β) levels, impaired ipsilateral hippocampal long-term potentiation (LTP) and induced anxiodepressive-like behaviours in a time-dependent manner in rodents. Pharmacological or optogenetic inhibition of ipsilateral hippocampal microglia completely blocked trigeminal neuralgia-induced anxiodepressive-like behaviours. Activation of unilateral hippocampal microglia directly elicited an anxiodepressive state and impaired hippocampal LTP. Knockdown of ipsilateral hippocampal P2X7 receptors prevented trigeminal neuralgia-induced microglial activation and anxiodepressive-like behaviours. Furthermore, we demonstrated that microglia-derived IL-1β mediated microglial activation-induced anxiodepressive-like behaviours and LTP impairment.

CONCLUSION AND IMPLICATIONS

These findings suggest that priming of microglia with ATP/P2X7 receptors in the ipsilateral hippocampus drives pain-related anxiodepressive-like behaviours via IL-1β. An asymmetric role of the bilateral hippocampus in trigeminal neuralgia-induced anxiety and depression was uncovered. The approaches targeting microglia and P2X7 signalling might offer novel therapies for trigeminal neuralgia-related anxiety and depressive disorder.

Outcomes of a QST Protocol in Healthy Subjects and Chronic Pain Patients: A Controlled Clinical Trial

Chronic pain is an important cause of disability with a high burden to society. Quantitative sensory testing (QST) is a noninvasive multimodal method used to discriminate the function of nerve fibers. The aim of this study is to propose a new, reproducible, and less time-consuming thermal QST protocol to help characterize and monitor pain. Additionally, this study also compared QST outcomes between healthy and chronic pain subjects. Forty healthy young/adult medical students and fifty adult/elderly chronic pain patients were evaluated in individual sessions including pain history, followed by QST assessments divided into three proposed tests: pain threshold, suprathreshold, and tonic pain. In the chronic pain group, a significantly higher pain threshold (hypoesthesia) and a higher pain sensibility (hyperalgesia) were demonstrated at threshold temperature when compared to healthy participants. The sensitivity to the suprathreshold and tonic stimulus did not prove to be significantly different between both groups. The main results demonstrated that the heat threshold QST tests can be helpful in evaluating hypoesthesia and that the sensitivity threshold temperature test can demonstrate hyperalgesia in individuals with chronic pain. In conclusion, this study demonstrates the importance of using tools such as QST as a complement to detect changes in several pain dimensions.

Environmental enrichment promotes resilience to neuropathic pain-induced depression and correlates with decreased excitability of the anterior cingulate cortex

Depression is a common comorbidity of chronic pain with many patients being affected. However, efficient pharmacological treatment strategies are still lacking. Therefore, it is desirable to find additional alternative approaches. Environmental enrichment has been suggested as a method to alleviate pain-induced depression. However, the neuronal mechanisms of its beneficial effects are still elusive. The anterior cingulate cortex (ACC) plays a central role in processing pain-related negative affect and chronic pain-induced plasticity in this region correlates with depressive symptoms. We studied the consequences of different durations of environmental enrichment on pain sensitivity and chronic pain-induced depression-like behaviors in a mouse model of neuropathic pain. Furthermore, we correlated the behavioral outcomes to the activity levels of pyramidal neurons in the ACC by analyzing their electrophysiological properties ex vivo. We found that early exposure to an enriched environment alone was not sufficient to cause resilience against pain-induced depression-like symptoms. However, extending the enrichment after the injury prevented the development of depression and reduced mechanical hypersensitivity. On the cellular level, increased neuronal excitability was associated with the depressive phenotype that was reversed by the enrichment. Therefore, neuronal excitability in the ACC was inversely correlated to the extended enrichment-induced resilience to depression. These results suggest that the improvement of environmental factors enhanced the resilience to developing chronic pain-related depression. Additionally, we confirmed the association between increased neuronal excitability in the ACC and depression-like states. Therefore, this non-pharmacological intervention could serve as a potential treatment strategy for comorbid symptoms of chronic pain.

LncRNA XR_351665 Contributes to Chronic Pain-Induced Depression by Upregulating DNMT1 via Sponging miR-152-3p

Chronic pain is frequently comorbid with depression. However, the mechanisms underlying chronic pain-induced depression remain unclear. Here, we found that DNA methyltransferase 1 (DNMT1) was upregulated in the central amygdala (CeA) of spared nerve injury (SNI)-induced chronic pain-depression rats, and knockdown of DNMT1 could improve the depression-like behaviors in SNI rats. Additionally, a panel of differentially expressed lncRNAs, including 38 upregulated and 12 downregulated lncRNAs, were identified by microarray analysis. Bioinformatics analysis suggested that the upregulated lncRNA XR_351665 was the upstream molecule to regulate DNMT1 expression. The knockdown of XR_351665 significantly alleviated the depression-like behaviors in SNI rats, whereas overexpression of XR_351665 induced the depression-like behaviors in naïve rats. Further mechanism-related researches uncovered that XR_351665 functioned as a competing endogenous RNA (ceRNA) to upregulate DNMT1 by competitively sponging miR-152-3p, and subsequently promoted the development of chronic pain-induced depression. Our findings suggest that lncRNA XR_351665 is involved in the development of chronic pain-induced depression by upregulating DNMT1 via sponging miR-152-3p. These data provide novel insight into understanding the pathogenesis of chronic pain-induced depression and identify a potential therapeutic target. PERSPECTIVE: LncRNA XR_351665 in CeA functions as a ceRNA to block the inhibitory effect of miR-152-3p on DNMT1 and contributes to the development of chronic pain-induced depression. These data suggest that manipulation of XR_351665/miR-152-3p/DNMT1 axis may be a potential method to attenuate chronic pain-induced depression.

Gallic Acid Improves Comorbid Chronic Pain and Depression Behaviors by Inhibiting P2X7 Receptor-Mediated Ferroptosis in the Spinal Cord of Rats

Ferroptosis is an inflammatory programmed cell death process that is dependent on iron deposition and lipid peroxidation. The P2X7 receptor not only is involved in the pain process but also is closely related to the onset of depression. Gallic acid (3,4,5-trihydroxybenzoic acid), which is naturally found in a variety of plants, exhibits anti-inflammatory, antioxidant, and analgesic effects. This study established a rat model with the comorbidity of chronic constrictive injury (CCI) plus chronic unpredictable mild stress (CUMS) to explore the role and mechanism of gallic acid in the treatment of pain and depression comorbidity. Our experimental results showed that pain and depression-like behaviors were more obvious in the chronic constriction injury (CCI) plus chronic unpredictable mild stimulation (CUMS) group than they were in the sham operation group, and the P2X7-reactive oxygen species (ROS) signaling pathway was activated. The tissue iron concentration was increased, and mitochondrial damage was observed in the CCI plus CUMS group. These results were alleviated with gallic acid treatment. Therefore, we speculate that gallic acid inhibits the ferroptosis of the spinal microglia by regulating the P2X7-ROS signaling pathway and relieves the behavioral changes in rats with comorbid pain and depression.

Examining sex differences in responses to footshock stress and the role of the metabotropic glutamate receptor 5: an [18F]FPEB and positron emission tomography study in rats

Clinical investigations suggest involvement of the metabotropic glutamate receptor 5 (mGluR5) in the pathophysiology of fear learning that underlies trauma-related disorders. Here, we utilized a 4-day fear learning paradigm combined with positron emission tomography (PET) to examine the relationship between mGluR5 availability and differences in the response of rats to repeated footshock exposure (FE). Specifically, on day 1, male (n = 16) and female (n = 12) rats received 15 footshocks and were compared with control rats who did not receive footshocks (n = 7 male; n = 4 female). FE rats were classified as low responders (LR) or high responders (HR) based on freezing to the context the following day (day 2). PET with [18F]FPEB was used to calculate regional mGluR5 binding potential (BPND) at two timepoints: prior to FE (i.e., baseline), and post-behavioral testing. Additionally, we used an unbiased proteomics approach to assess group and sex differences in prefrontal cortex (PFC) protein expression. Post-behavioral testing we observed decreased BPND in LR females, but increased BPND in HR males relative to baseline. Further, individuals displaying the greatest freezing during the FE context memory test had the largest increases in PFC BPND. Males and females displayed unique post-test molecular profiles: in males, the greatest differences were between FE and CON, including upregulation of mGluR5 and related molecular networks in FE, whereas the greatest differences among females were between the LR and HR groups. These findings suggest greater mGluR5 availability increases following footshock exposure may be related to greater contextual fear memory. Results additionally reveal sex differences in the molecular response to footshock, including differential involvement of mGluR5-related molecular networks.

Examining mGlu5 Receptor Availability as a Predictor of Vulnerability to PTSD: An [18F]FPEB and PET Study in Male and Female Rats

Background

Females are twice as likely to experience post-traumatic stress disorder (PTSD) than males, yet specific factors contributing to this greater risk are not fully understood. Our clinical and recent preclinical findings suggest a role for the metabotropic glutamate receptor 5 (mGlu5) in PTSD and differential involvement between males and females.

Methods

Here, we further investigate whether mGlu5 receptor availability may contribute to individual and sex differences in PTSD susceptibility by quantifying receptor availability using the mGlu5 receptor-specific radiotracer, [18F]FPEB, and positron emission tomography in male (n = 16) and female (n = 16) rats before and after traumatic footshock exposure (FE) and assessment of stress-enhanced fear learning (SEFL) susceptibility, as compared with no-shock controls (CON; n = 7 male; n = 8 female).

Results

Overall, FE rats displayed greater fear generalization as compared with CON (p < .001). Further, greater mGlu5 receptor availability at baseline (p = .003) and post-test (p = .005) was significantly associated with expression of the SEFL phenotype. Notably, FE female rats displayed a shift to more passive coping (ie, freezing), and displayed greater SEFL susceptibility (p = .01), and had lower baseline mGlu5 availability (p = .03) relative to their FE male rat counterparts.

Conclusion

Results are consistent with clinical findings of higher mGlu5 receptor availability in PTSD, and add to growing evidence implicating these receptors in the pathophysiology of PTSD and sex-differences in susceptibility for this disorder.

From Low-Grade Inflammation in Osteoarthritis to Neuropsychiatric Sequelae: A Narrative Review

Nowadays, osteoarthritis (OA), a common, multifactorial musculoskeletal disease, is considered to have a low-grade inflammatory pathogenetic component. Lately, neuropsychiatric sequelae of the disease have gained recognition. However, a link between the peripheral inflammatory process of OA and the development of neuropsychiatric pathology is not completely understood. In this review, we provide a narrative that explores the development of neuropsychiatric disease in the presence of chronic peripheral low-grade inflammation with a focus on its signaling to the brain. We describe the development of a pro-inflammatory environment in the OA-affected joint. We discuss inflammation-signaling pathways that link the affected joint to the central nervous system, mainly using primary sensory afferents and blood circulation via circumventricular organs and cerebral endothelium. The review describes molecular and cellular changes in the brain, recognized in the presence of chronic peripheral inflammation. In addition, changes in the volume of gray matter and alterations of connectivity important for the assessment of the efficacy of treatment in OA are discussed in the given review. Finally, the narrative considers the importance of the use of neuropsychiatric diagnostic tools for a disease with an inflammatory component in the clinical setting.

Progress in the mechanism of acupuncture intervention on pain emotion and pain cognition mediated by limbic system

Pain is a complex physiological and psychological activity, involving at least three dimensions, including pain sensation, pain emotion, and pain cognition. Acupuncture can clearly relieve the pain sensation of patients and improve pain emotion and pain cognition induced by pain; acupuncture participates in the multi-dimensional regulation of pain through brain regions of the limbic system such as anterior cingulate cortex (ACC), amygdala (AMY), and hippocampus. By analyzing relevant literature, it has been found that the regulation of acupuncture on pain emotion is mainly related to the activation of pertinent opioid receptors in the ACC, the decrease of the expression of extracellular signal-regulated kinase (ERK), and the promotion of the expression of glutamic acid (Glu) A1, metabotropic glutamate receptor-1 (mGluR1), and γ-aminobutyric acid aminobutyric acid (GABA) B2 protein in the AMY. The regulation of acupuncture on pain cognition is mainly related to the elevation of the expression of protein kinase A (PKA) and phospho-p38 mitogen-activated protein kinase (phospho-p38 MAPK) and the inhibition of cyclic adenosine monophosphate (cAMP)/PKA/cAMP response element-binding protein (CREB) signaling pathway in the ACC.

The effects of osteopathic manipulative treatment on pain and disability in patients with chronic neck pain: A single-blinded randomized controlled trial

BACKGROUND

Neck pain (NP) affects up to 70% of individuals at some point in their lives. Systematic reviews indicate that manual treatments can be moderately effective in the management of chronic, nonspecific NP. However, there is a paucity of studies specifically evaluating the efficacy of osteopathic manipulative treatment (OMT).

OBJECTIVE

To evaluate the efficacy of OMT in reducing pain and disability in patients with chronic NP.

DESIGN

Single-blinded, cross-over, randomized-controlled trial.

SETTING

University-based, osteopathic manipulative medicine outpatient clinic.

PARTICIPANTS

Ninety-seven participants, 21 to 65 years of age, with chronic, nonspecific NP.

INTERVENTIONS

Participants were randomized to two trial arms: immediate OMT intervention or waiting period first. The intervention consisted of three to four OMT sessions over 4 to 6 weeks, after which the participants switched groups.

MAIN OUTCOME MEASURES

Primary outcome measures were pain intensity (average and current) on the numerical rating scale and Neck Disability Index. Secondary outcomes included Patient-Reported Outcomes Measurement Information System-29 (PROMIS-29) health domains and Fear Avoidance Beliefs Questionnaire. Outcomes obtained prior to the cross-over allocation were evaluated using general linear models and after adjusting for baseline values.

RESULTS

A total of 38 and 37 participants were available for the analysis in the OMT and waiting period groups, respectively. The results showed significantly better primary outcomes in the immediate OMT group for reductions in average pain (-1.02, 95% confidence interval [CI] -1.72, -0.32; p = .005), current pain (-1.02, 95% CI -1.75, -0.30; p = .006), disability (-5.30%, 95% CI -9.2%, -1.3%; p = .010) and improved secondary outcomes (PROMIS) related to sleep (-3.25, 95% CI -6.95, -1.54; p = .003), fatigue (-3.26, 95% CI -6.04, -0.48; p = .022), and depression (-2.59, 95% CI -4.73, -0.45; p = .018). The effect sizes were in the clinically meaningful range between 0.5 and 1 standard deviation. No study-related serious adverse events were reported.

CONCLUSIONS

OMT is relatively safe and effective in reducing pain and disability along with improving sleep, fatigue, and depression in patients with chronic NP immediately following treatment delivered over approximately 4 to 6 weeks.

The genetic structure of pain in depression patients: A genome-wide association study and proteome-wide association study

BACKGROUND

Comparing with the general population, the pain in depression patients has more complex biological mechanism. We aim to explore the etiological mechanism of pain in depression patients from the perspective of genetics.

METHODS

Utilizing the UK Biobank samples with self-reported depression status or PHQ score ≥10, we conducted genome-wide association studies (GWAS) of seven pain traits (N = 1,133-58,349). Additionally, we used FUSION pipeline to perform proteome-wide association study (PWAS) and transcriptome-wide association study (TWAS) by integrating GWAS summary data with two different proteome reference weights (ROS/MAP and Banner) and Rnaseq gene expression reference weights, respectively.

RESULTS

GWAS identified 3 significant genes associated with different pain traits in depression patients, including TRIOBP (P_GWAS = 4.48 × 10^-8) for stomach or abdominal pain, SLC9A9(P_GWAS = 2.77 × 10^-8) for multisite chronic pain (MCP) and ADGRF1 (P_GWAS = 1.51 × 10^-8) for neck or shoulder pain. In addition, PWAS and TWAS analysis also identified multiple candidate genes associated with different pain traits in depression patients, such as TPRG1L (P_PWAS-Banner = 3.38 × 10^-2) and SIRPA (P_PWAS-Banner = 3.65 × 10^-2) for MCP, etc. Notably, when comparing the results of PWAS and TWAS analysis, we found overlapping candidate genes in these pain traits, such as GSTM3 (P_PWAS-_Banner = 3.38 × 10^-2, P_TWAS = 6.92 × 10^-3) in the stomach or abdominal pain phenotype, ATG7 (P_PWAS-_Rosmap = 3.15 × 10^-2, P_TWAS = 2.98 × 10^-2) in the MCP, etc. CONCLUSIONS: We identified multiple novel candidate genes for pain traits in depression patients from different perspectives of genetics, which provided novel clues for understanding the genetic mechanisms underlying the pain in depression patients.

Chronic Unpredictable Mild Stress Model of Depression: Possible Sources of Poor Reproducibility and Latent Variables

Major depressive disorder (MDD) is one of the most common mood disorders worldwide. A lack of understanding of the exact neurobiological mechanisms of depression complicates the search for new effective drugs. Animal models are an important tool in the search for new approaches to the treatment of this disorder. All animal models of depression have certain advantages and disadvantages. We often hear that the main drawback of the chronic unpredictable mild stress (CUMS) model of depression is its poor reproducibility, but rarely does anyone try to find the real causes and sources of such poor reproducibility. Analyzing the articles available in the PubMed database, we tried to identify the factors that may be the sources of the poor reproducibility of CUMS. Among such factors, there may be chronic sleep deprivation, painful stressors, social stress, the difference in sex and age of animals, different stress susceptibility of different animal strains, handling quality, habituation to stressful factors, various combinations of physical and psychological stressors in the CUMS protocol, the influence of olfactory and auditory stimuli on animals, as well as the possible influence of various other factors that are rarely taken into account by researchers. We assume that careful inspection of these factors will increase the reproducibility of the CUMS model between laboratories and allow to make the interpretation of the obtained results and their comparison between laboratories to be more adequate.

Microglia senescence is related to neuropathic pain-associated comorbidities in the spared nerve injury model

ABSTRACT

The increased presence of senescent cells in different neurological diseases suggests the contribution of senescence in the pathophysiology of neurodegenerative disorders. Microglia can adapt to any type of disturbance of the homeostasis of the central nervous system (CNS) and its altered activity can lead to permanent and unresolvable damage. The aim of this work was to characterize the behavioural phenotype of spared nerve injury (SNI) mice and then associate it to senescence-related mechanisms. In this work we investigated the timing of the onset of anxiety, depression, or memory decline associated with peripheral neuropathic pain, and their correlation with the presence of microglial cellular senescence. SNI mice showed a persistent pain hypersensitivity from 3 days after surgery. 28 days after nerve injury they also developed anxiety, depression, and cognitive impairment. The appearance of these symptoms was coincident to a significant increase of senescence markers, such as β-galactosidase and senescent-associated secretory phenotype (SASP), at microglial level in the spinal cord and hippocampus of SNI animals. These markers were unaltered at previous time points. In murine immortalized microglial cells (BV2) stimulated with LPS 500 ng/mL for 10 days (4h/day) every other day, we observed an increase of β-galactosidase, SASP appearance, a reduction of cell viability and an increase of Senescence-Associated Heterochromatic Foci (SAHF). Therefore, present findings could represent an important step to a better understanding of the pathophysiological cellular mechanisms in comorbidities related to neuropathic pain states.

Effect and safety of extracorporeal shockwave therapy for postherpetic neuralgia: A randomized single-blind clinical study

Objective

To evaluate the efficacy and safety of extracorporeal shockwave therapy (ESWT) for postherpetic neuralgia.

Design

Randomized single-blind clinical study.

Patients

Patients with postherpetic neuralgia.

Methods

Patients were randomly divided into the control group and the ESWT group. The control group received conventional treatment while the ESWT group received conventional treatment and ESWT. The primary outcome is pain degree as assessed by the numeric rating scale (NRS), and secondary outcomes include brief pain inventory (BPI), Self-rating Anxiety Scale (SAS), Self-rating Depression Scale (SDS), and Pittsburgh Sleep Quality Index (PSQI). Data were collected at baseline and at weeks 1, 4, and 12. Linear mixed-effects models were applied to repeated measurement data.

Results

The scores on the NRS, BPI, SAS, SDS, and PSQI decreased over time in both groups. The NRS and SDS scores of the ESWT group were statistically lower than the control group. There was no time × group interaction in the mixed model analysis. Baseline age was correlated with NRS scores and BPI scores, and invasive treatment was related to PSQI scores, with no interaction effect for baseline confounders observed. No adverse events were observed during the process of this trial.

Conclusion

Extracorporeal shockwave therapy combined with conventional treatment could relieve pain and improve the psychological state in patients with postherpetic neuralgia without serious adverse effects.

Systematic Review and Meta-Analysis of High-Frequency rTMS over the Dorsolateral Prefrontal Cortex .on Chronic Pain and Chronic-Pain-Accompanied Depression

The effect of high-frequency (HF) repetitive transcranial magnetic stimulation (rTMS) on the dorsolateral prefrontal cortex (DLPFC) can relieve chronic pain and accompanying depressive symptoms. However, in recent years, some high-quality studies have challenged this view. Therefore, it is necessary to update the data and analyze the effects of HF rTMS on the DLPFC on chronic pain and accompanying depression. We performed a systematic review and meta-analysis to evaluate the effect of HF rTMS on the DLPFC on chronic pain and accompanying depression. We searched PubMed, Medline, Web of Science, and Cochrane through September 2021. The search strings searched were : "pain" AND ("TMS" OR "transcranial magnetic stimulation") AND "prefrontal cortex". The inclusion criteria according to PICOS was as follows: P, patient with chronic pain; I, HF (≥5 Hz) rTMS on the DLPFC; C, included a sham treatment condition; O, pain indicators; S, pre-/poststudies, crossover, or parallel-group. We extracted the pain and accompanying depression evaluation indicators. The short-term analgesic effect of HF rTMS over the left DLPFC is not significant (WMD = 0.34, 95% CI: [-1.60, 2.28]) but has a significant mid-term and long-term analgesic effect on chronic pain (WMD = -0.50, 95% CI: [-0.99, -0.01]; WMD = -1.10, 95% CI: [-2.00, -0.19], respectively). HF rTMS over the DLPFC can effectively alleviate the depressive symptoms of patients with chronic pain (WMD = -0.83, 95% CI: [-3.01, 1.36]). Thus, HF rTMS on the left DLPFC can relieve chronic pain and accompanying depressive symptoms.

Sex-dependent effects of postweaning exposure to an enriched environment on visceral pain and anxiety- and depression-like behaviors induced by neonatal maternal separation

BACKGROUND

Neonatal maternal separation (NMS) can lead to visceral pain and anxiety- and depression-like behaviors. An enriched environment (EE) can alleviate NMS-induced pain and mental disorders, but previous studies have mostly been performed in male animals. Therefore, the aim of this study was to investigate whether the effects of EE were sex dependent at different stages of development.

METHODS

Female and Male C57BL/6 J mice that had been subjected to NMS alone and those subjected to both NMS and exposed to EE were used in this study. The visceral pain threshold test (PTT), open field test (OFT), sucrose preference test (SPT), and forced swimming test (FST) were conducted to evaluate visceral pain, anxiety-like behavior, and depression-like behavior in mice, respectively.

RESULTS

Compared with the male mice in the NMS group without EE exposure, those exposed to EE from postnatal day (P)21 to 41 showed an increase of the visceral pain threshold in the PTT, an increase of the central time and central distance in the OFT, an increase of the sucrose preference rate in the SPT, and a decrease of the time of immobility in the FST. Compared with both female and male mice in the NMS group without EE exposure, those exposed to EE from P21 to P61 had an increase of the visceral pain threshold in the PTT, an increase of the central time and central distance in the OFT, an increase in the sucrose preference rate in the SPT, and a decrease of the time of immobility in the FST.

CONCLUSIONS

EE is more effective in male NMS mice, while longer EE is required in female NMS mice for positive effects.

In the Shoulder or in the Brain? Behavioral, Psychosocial and Cognitive Characteristics of Unilateral Chronic Shoulder Pain with Symptoms of Central Sensitization

The recognition of central sensitization (CS) is crucial, as it determines the results of rehabilitation. The aim of this study was to examine associations between CS and catastrophizing, functionality, disability, illness perceptions, kinesiophobia, anxiety, and depression in people with chronic shoulder pain (SP). In this cross-sectional study, 64 patients with unilateral chronic SP completed a few questionnaires including the Central Sensitization Inventory, the Oxford Shoulder Score, the Tampa Scale for Kinesiophobia, the Hospital Anxiety and Depression Scale, the Pain Catastrophizing Scale, the Brief Illness Perception Questionnaire and the “arm endurance” test. On the basis of three constructed linear regression models, it was found that pain catastrophizing and depression (model 1: p < 0.001, R = 0.57, R2 = 0.33), functionality (model 2: p < 0.001, R = 0.50, R2 = 0.25), and helplessness (model 3: p < 0.001, R = 0.53, R2 = 0.28) were significant predictors for CS symptoms in chronic SP. Two additional logistic regression models also showed that depression (model 4: p < 0.001, Nagelkerke R2 = 0.43, overall correct prediction 87.5%) and functionality (model 5: p < 0.001, Nagelkerke R2 = 0.26, overall correct prediction 84.4%) can significantly predict the classification of chronic SP as centrally sensitized. Patients who were classified as centrally sensitized (n = 10) were found to have significantly worse functionality, psychological factors (anxiety, depression, kinesiophobia, catastrophizing), and pain intensity (p < 0.05). Catastrophizing, depression, and functionality are predictive factors of CS symptoms in patients with chronic shoulder pain. Health care providers should adopt a precision medicine approach during assessment and a holistic rehabilitation of patients with unilateral chronic SP.

Long-term neuropathic pain behaviors correlate with synaptic plasticity and limbic circuit alteration: a comparative observational study in mice

ABSTRACT

Neuropathic pain has long-term consequences in affective and cognitive disturbances, suggesting the involvement of supraspinal mechanisms. In this study, we used the spared nerve injury (SNI) model to characterize the development of sensory and aversive components of neuropathic pain and to determine their electrophysiological impact across prefrontal cortex and limbic regions. Moreover, we evaluated the regulation of several genes involved in immune response and inflammation triggered by SNI. We showed that SNI led to sensorial hypersensitivity (cold and mechanical stimuli) and depressive-like behavior lasting 12 months after nerve injury. Of interest, changes in nonemotional cognitive tasks (novel object recognition and Y maze) showed in 1-month SNI mice were not evident normal in the 12-month SNI animals. In vivo electrophysiology revealed an impaired long-term potentiation at prefrontal cortex-nucleus accumbens core pathway in both the 1-month and 12-month SNI mice. On the other hand, a reduced neural activity was recorded in the lateral entorhinal cortex-dentate gyrus pathway in the 1-month SNI mice, but not in the 12-month SNI mice. Finally, we observed the upregulation of specific genes involved in immune response in the hippocampus of 1-month SNI mice, but not in the 12-month SNI mice, suggesting a neuroinflammatory response that may contribute to the SNI phenotype. These data suggest that distinct brain circuits may drive the psychiatric components of neuropathic pain and pave the way for better investigation of the long-term consequences of peripheral nerve injury for which most of the available drugs are to date unsatisfactory.

Maternal pain during pregnancy dose-dependently predicts postpartum depression: The Japan Environment and Children's Study

BACKGROUND

Postpartum depression (PPD) affects women during the first year after delivery. This study investigated the association between prenatal pain (maternal pain during pregnancy) and PPD.

METHODS

Data were analyzed from the Japan Environment and Children's Study (JECS), a nationwide prospective birth cohort study. Information on prenatal pain was collected twice during pregnancy through self-administered questionnaires. PPD symptoms were assessed using the Edinburgh Postnatal Depression Scale at one month postpartum. Poisson regression analyses were performed to investigate the association between prenatal pain and PPD, with other putative risk factors adjusted in the model.

RESULTS

Among 84,801 study subjects, 11,535 (13.6%) were screened as positive for PPD. In the present study, the occurrence of prenatal pain was 69.6 and 84.0% at the first trimester and the second/third trimester, respectively. A positive relationship between any degree of pain and PPD in both the first and the second/third trimester was observed. A significant linear dose-dependent association was also found (Ptrend < 0.001) when the subjects were divided by the severity of pain. Using participants without any pain at either point as a reference, those with persistent pain both at the first and the second/third trimesters showed the highest risk for PPD: aRR = 1.95 (95%CI: 1.76-2.15; p < 0.001).

LIMITATIONS

No detailed information regarding the type or site of prenatal pain was available in the JECS questionnaires, neither did data concerning delivery and postpartum pain.

CONCLUSIONS

The study results suggest that prenatal pain is a dose-dependent risk factor for the development of PPD.

Comprehensive Preclinical Assessment of Sensory, Functional, Motivational-Affective, and Neurochemical Outcomes in Neuropathic Pain: The Case of the Sigma-1 Receptor

Chronic pain remains a major health problem and is currently facing slow drug innovation. New drug treatments should address not only the sensory-discriminative but also functional and motivational-affective components of chronic pain. In a mouse model of neuropathic pain induced by partial sciatic nerve ligation (PSNL), we analyzed sensory and functional-like outcomes by hindpaw mechanical stimulation and automated gait analysis (CatWalk). We characterized over time a reward-seeking task based on diminished motivation for natural reinforcers (anhedonic-like behavior). To differentiate the appetitive ("wanting") and consummatory ("liking") aspects of motivational behavior, we quantified the latency and number of approaches to eat white chocolate, as well as the eating duration and amount consumed. We explored a putative chronic pain-induced dysregulation of monoamine function by measuring monoamine levels in the nucleus accumbens (NAc), a well-known brain reward area. Finally, we investigated the role of sigma-1 receptor (σ₁R) modulation, a nonopioid target, in these multiple dimensions by genetic deletion and pharmacological dose-response studies. After 6 weeks, PSNL increased the approach latency and reduced the consumption of white chocolate in 20-25% of the mice, while around 50-60% had one or the other parameter affected independently. After 10 weeks, sham-operated mice also displayed anhedonic-like behavior. PSNL was associated with reduced extracellular baseline dopamine and increased norepinephrine in the NAc and with a suppression of increased dopamine and serotonin efflux in response to the rewarding stimulus. Genetic and pharmacological blockade of σ₁R relieved these multiple alterations in nerve-injured mice. We comprehensively describe sensory, functional, and depression-like impairment of key components of motivated behavior associated with nerve injury. We provide a neurochemical substrate for the depressed mesocorticolimbic reward processing in chronic pain, with a potentially increased translational value. Our results also highlight σ₁R for the therapeutic intervention of neuropathic pain.

Influence of Cerebral Glucose Metabolism by Chronic Pain-Mediated Cognitive Impairment in Adolescent Rats

Chronic pain during adolescence can lead to mental health disorders in adulthood, but the underlying mechanism is still unclear. Furthermore, the homeostasis of cerebral glucose metabolism and neurotransmitter metabolic kinetics are closely associated with cognitive development and pain progression. The present study investigated changes in cognitive function and glucose metabolism in adult rats, which had experienced chronic pain during their adolescence. Here, spared nerve injury (SNI) surgery was conducted in 4-week-old male rats. Mechanical nociceptive reflex thresholds were analyzed, and SNI chronic pain (SNI-CP) animals were screened. Based on animal behavioral tests (open field, three-chambered social, novel object recognition and the Y maze), the SNI-CP animals showed learning and memory impairment and anxiety-like behaviors, compared to SNI no chronic pain (SNI-NCP) animals. The cerebral glucose metabolism in the prefrontal cortex and hippocampus of adult SNI-CP animals was decreased with positron emission tomography/computed tomography. GABA₂ and Glu₄ levels in the metabolic kinetics study were significantly decreased in the hippocampus, frontal cortex, and temporal cortex, and the expression of GLUT3 and GLUT4 was also significantly downregulated in the prefrontal cortex and hippocampus of adult rats in the SNI-CP group. These findings suggest that the rats which suffered chronic pain during adolescence have lower cerebral glucose metabolism in the cortex and hippocampus, which could be related to cognitive function during the development of the central nervous system.

Analysis of Antidepressant, Benzodiazepine Anxiolytic, and Hypnotic Use When Treating Depression, Anxiety, and Aggression in Pain Clinic Patients Treated for Neuropathic Pain

Depression, anxiety, and aggression accompany neuropathic pain. Effective treatment of these comorbidities enhances the outcomes of pain management. Therefore, the study was designed to analyze the relationship between the intensity of depression, anxiety, and aggression and the pharmacotherapy applied in the daily practice of treating neuropathic pain. The aim of the study was to evaluate the frequency of using antidepressants (ADs), benzodiazepine anxiolytics (BDAs), and hypnotics, and the influence of administering these on the intensity of depression, anxiety, and aggression in patients diagnosed with neuropathic pain. A multi-center survey was conducted among 421 patients. An evaluation of the severity of depression, anxiety, and aggression was made using the Hospital Anxiety and Depression Scale—Modified Version (HADS-M). Among the patients treated due to neuropathic pain, ADs are used much more often than BDAs and hypnotics. Depression was well controlled, while anxiety was identified as a possible uncontrolled therapeutic problem in these patients, despite the correlation between the frequency of AD and hypnotics usage and the severity of anxiety. We also found that women show a higher level of intensity in both anxiety and depression, but this does not influence the frequency of their being administered ADs, BDAs, and hypnotics.

Reciprocal interaction between depression and pain: results from a comprehensive bidirectional Mendelian randomization study and functional annotation analysis

ABSTRACT

To understand a putative causal link for depression and pain, we retrieved summary statistics from genome-wide association studies conducted for pain at 7 different body sites (N = 151,922-226,683) and major depression disorder (MDD, Ncase/control = 246,363/561,190). We conducted a bidirectional Mendelian randomization analysis using distinct genome-wide association studies-identified single nucleotide polymorphisms for each trait as instrumental variables and performed several sensitivity analyses to verify Mendelian randomization assumptions. We also conducted functional annotation analysis using 396 tissue-specific annotations from the roadmap project. Across 7 different body sites, genetic predisposition to depression was associated with pain at the neck/shoulder (odds ratio [OR] = 1.08 per one log-unit increase in depression risk, 95% confidence interval [CI]: 1.06-1.10), back (OR = 1.05, 95% CI: 1.04-1.07), abdominal/stomach (OR = 1.03, 95% CI: 1.02-1.04), as well as headache (OR = 1.10, 95% CI: 1.07-1.12), but not with pain on the face, hip, and knee. In the reverse direction, genetically instrumented multisite chronic pain (OR = 1.78 per one increment in the number of pain site, 95% CI: 1.51-2.11) and headache (OR = 1.55 per one log-unit increase in headache risk, 95% CI = 1.13-2.10) were associated with MDD. Functional annotation analysis showed differential clustering patterns where depression clustered closely with headache and neck/shoulder pain, exhibiting substantial brain tissue enrichment. Our study indicates that depression is a causal risk factor for headache and pain localized at neck/shoulder, back, and abdominal/stomach, rather than pain at face, hip, and knee, and suggests common neurological pathologies underlying the development of depression, headache, and neck/shoulder pain.

Low back pain: biopsychosocial aspects of chronic and acute pain

Abstract: Chronic low back pain is a highly prevalent pathology, which has unclear associations with psychosocial aspects. This study investigated differences between patients with chronic low back pain (n = 25) and acute low back pain (n = 20) and verified the effect of the variables assessed on the pain mean. The design was cross-sectional, and the instruments applied were: sociodemographic interviews, Brief Pain Inventory, Beck Depression Inventory II, Hamilton Anxiety Rating Scale, Personality Factor Battery, Social Support Scale and Pain Catastrophizing Scale. The chronic pain group had significantly higher means of pain intensity, anxiety and catastrophic thoughts. In the regression analysis, the factor Depression of the Personality Factor Battery and belonging to the chronic pain group were found as predictors of the mean pain in the sample studied. It is understood that psychological factors are associated with the pain condition and require further investigation.

Plantar fascial fibromatosis and herpes zoster

Purpose

Infection, chronic pain and depression are considered risk factors for herpes zoster (HZ). However, the correlation between plantar fascial fibromatosis (PFF) and HZ remains unknown. This study investigated HZ risk in patients with PFF.

Methods

Data was extracted from the Longitudinal Health Insurance Database 2000, which is a subsample of the Taiwan National Health Insurance (NHI) Research Database and contains 1 million NHI beneficiaries. Between 2000 and 2012, patients diagnosed as having PFF were included in the case cohort. Every case was age and sex-matched with individuals without PFF through 1:4 frequency matching (control cohort). The end of the follow-up was defined as December 31, 2013, the date of HZ diagnosis, death, emigration, or withdrawal from the NHI program.

Results

In total, 4,729 patients were diagnosed as having PFF and were matched with 18,916 individuals without PFF. Patients with PFF were 1.23 times more likely to develop HZ than were those without PFF. Among those aged ≥65 years, patients with PFF had a higher HZ risk than did those without PFF (adjusted hazard ratio [aHR] = 1.48). Men with PFF had a significantly higher risk of HZ than did men without PFF (aHR = 1.44).

Conclusion

Patients with PFF, particularly older and male patients, having a high HZ risk and may thus be vaccinated for HZ.

Pulsed Radiofrequency Upregulates Serotonin Transporters and Alleviates Neuropathic Pain-Induced Depression in a Spared Nerve Injury Rat Model

Neuropathic pain (NP) is difficult to treat due to complex pathophysiological mechanisms. Pulsed radiofrequency (RRF) has been used widely with neuromodulation effect in refractory chronic pain treatment. A recent study found that PRF treatment may decrease chronic pain-related anxiety-depressant symptoms in patients, even though the mechanisms are unclear. Additionally, accumulated evidence has shown serotonin uptake is correlated with various neuropsychiatric diseases. Therefore, we investigated the effects and underlying mechanisms of PRF on depression-like behaviors, resulting from spared nerve injury (SNI)-induced NP. We examined the indexes of mechanical allodynia, cold allodynia, depression-like behavior, and blood cytokines by dynamic plantar aesthesiometry, acetone spray test, forced swimming test, and ProcartaPlex multiplex immunoassays in male Wistar rats, respectively. Serotonin transporters (SERTs) in rat brains were examined by using 4-[18F]-ADAM/PET imaging. We found that specific uptake ratios (SURs) of SERTs were significantly decreased in the brain regions of the thalamus and striatum in rats with SNI-induced NP and depression-like behaviors. Additionally, the decrease in SERT density was correlated with the development of a depression-like behavior indicated by the forced swimming test results and pronounced IL-6 cytokines. Moreover, we demonstrated that PRF application could modulate the descending serotoninergic pathway to relieve pain and depression behaviors.

Time Course of Homeostatic Structural Plasticity in Response to Optogenetic Stimulation in Mouse Anterior Cingulate Cortex

Plasticity is the mechanistic basis of development, aging, learning, and memory, both in healthy and pathological brains. Structural plasticity is rarely accounted for in computational network models due to a lack of insight into the underlying neuronal mechanisms and processes. Little is known about how the rewiring of networks is dynamically regulated. To inform such models, we characterized the time course of neural activity, the expression of synaptic proteins, and neural morphology employing an in vivo optogenetic mouse model. We stimulated pyramidal neurons in the anterior cingulate cortex of mice and harvested their brains at 1.5 h, 24 h, and $48\,\mathrm{h}$ after stimulation. Stimulus-induced cortical hyperactivity persisted up to 1.5 h and decayed to baseline after $24\,\mathrm{h}$ indicated by c-Fos expression. The synaptic proteins VGLUT1 and PSD-95, in contrast, were upregulated at $24\,\mathrm{h}$ and downregulated at $48\,\mathrm{h}$, respectively. Spine density and spine head volume were also increased at $24\,\mathrm{h}$ and decreased at $48\,\mathrm{h}$. This specific sequence of events reflects a continuous joint evolution of activity and connectivity that is characteristic of the model of homeostatic structural plasticity. Our computer simulations thus corroborate the observed empirical evidence from our animal experiments.

Bibliometric Analysis of Studies on Neuropathic Pain Associated With Depression or Anxiety Published From 2000 to 2020

Objective: Neuropathic pain (NP) associated with depression or anxiety is highly prevalent in clinical practice. Publications about NP associated with depression or anxiety increased exponentially from 2000 to 2020. However, studies that applied the bibliometric method in analyzing global scientific research about NP associated with depression or anxiety are rare. This work used the bibliometric method to analyze the publications on NP associated with depression or anxiety between 2000 and 2020. Method: Publications from 2000 and 2020 were identified from the Thomson Reuters Web of Science (WoS) database. We employed CiteSpace V to conduct the bibliometric study. Results: A total of 915 articles or reviews were obtained from the WoS database. The number of publications has increased over the last two decades. The USA was the most productive among countries or regions in the field. According to the burst key words, neuroinflammation, hippocampus, safety, and modulation were the hot global research issues in the domain. Conclusion: Publications about NP associated with depression or anxiety have remarkably increased from 2000 to 2020. These historical opinions about NP associated with depression or anxiety could be an important practical basis for further research into potential development trends.

Prolonged parent-child separation and pain in adolescence: The role of HPA-axis genetic variations

BACKGROUND

Increasing evidence has demonstrated that childhood adversity was a predictor of pain and hypothalamic-pituitary-adrenal (HPA) axis genetic variation is associated with pain risk. This study aims to explore possible effects of prolonged childhood separation from parents and HPA polygenic risk score (PRS) on pain among adolescents in rural China.

METHOD

We used data from 219 adolescents in rural area of Fuyang city, Anhui province, China. Parent-child separation was collected through interview and pain intensity was reported using the 11-point Numerical Rating Scale. SNP genotyping was performed using an improved multiplex ligation detection reaction (iMLDR) technique. The PRS was computed based on 3 single nucleotide polymorphisms (SNPs) in 2 genes (FKBP5 and NR3C1) related to HPA-axis stress reactivity.

RESULTS

Pain among adolescents separated from both parents scored higher compared to those without parent-child separation, however, this association was only observed in adolescents with moderate to high tertiles of PRS groups (parent-child separation in moderate group vs. no parent-child separation in moderate group: 3.07 vs. 1.57, P < 0.001; parent-child separation in highest group vs. no parent-child separation in highest group: 3.02 vs. 1.26, P < 0.001; parent-child separation in lowest group vs. no parent-child separation in lowest group: 2.34 vs. 1.25, P = 0.225). After controlled for demographic characteristics, psychopathological symptoms, adverse childhood experiences, parental warmth, prolonged childhood parent-child separation increased pain scores by 1.52 points (95% CI:0.72, 2.33) and 1.72 points (95% CI:1.13, 2.31) in moderate and high PRS groups, respectively.

CONCLUSION

Our findings suggest that adolescents separated from both parents while carrying more risk alleles related to HPA-axis stress reactivity are at heightened risk of pain.