Twin studies of the covariation of pain with depression and anxiety: A systematic review and re-evaluation of critical needs

Effect of intramuscular diazepam infusion on herpes zoster-related pain in older patients: a randomized, double-blind, placebo-controlled trial

OBJECTIVES

This study evaluated the effectiveness, psychological effects, and sleep quality using intramuscular diazepam infusion compared with placebo in patients with herpes zoster (HZ)-related pain.

METHODS

The patients were randomized to either the diazepam or control group. The diazepam group received an intramuscular injection of diazepam for 3 consecutive days, while the control group received an intramuscular injection of 0.9% normal saline. The primary outcome was pain relief on posttreatment day 4, as measured using the Visual Analog Scale (VAS). Moreover, anxiety and depression were evaluated using the Generalized Anxiety Disorder-7 (GAD7) and Patient Health Questionnaire-9 (PHQ9), respectively. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI).

RESULTS

In total, 78 patients were enrolled in the trial. The mean differences in VAS scores between the two groups were 0.62 (P = 0.049) on posttreatment day 3 and 0.66 (P = 0.037) on posttreatment day 4. The effective rates of pain management in the diazepam group ranged from 10.26 to 66.67%, which were higher than those in the control group on posttreatment days 3 and 4 (P < 0.05). The mean difference in PSQI scores between the diazepam and control groups was 1.36 (P = 0.034) on posttreatment day 7. No differences were found in the incidence of analgesia-adverse 1reactions between the diazepam and placebo groups.

CONCLUSIONS

The intramuscular injection of diazepam for 3 consecutive days provides effective pain management and improves the quality of life. Our study suggests that diazepam is more effective than the placebo in patients with HZ-related pain.

TRIAL REGISTRATION

The study was prospectively registered at https://www.isrctn.com/trialist(Registration date: 24/01/2018; Trial ID: ISRCTN12682696).

Trim14-IκBα Signaling Regulates Chronic Inflammatory Pain in Rats and Osteoarthritis Patients

Chronic inflammatory pain is the highest priority for people with osteoarthritis when seeking medical attention. Despite the availability of NSAIDs and glucocorticoids, central sensitization and peripheral sensitization make pain increasingly difficult to control. Previous studies have identified the ubiquitination system as an important role in the chronic inflammatory pain. Our study displayed that the E3 ubiquitin ligase tripartite motif-containing 14 (Trim14) was abnormally elevated in the serum of patients with osteoarthritis and pain, and the degree of pain was positively correlated with the degree of Trim14 elevation. Furthermore, CFA-induced inflammatory pain rat model showed that Trim14 was significantly increased in the L3-5 spinal dorsal horn (SDH) and dorsal root ganglion (DRG), and in turn the inhibitor of nuclear factor Kappa-B isoform α (IκBα) was decreased after Trim14 elevation. After intrathecal injection of Trim14 siRNA to inhibit Trim14 expression, IκBα expression was reversed and increased, and the pain behaviors and anxiety behaviors of rats were significantly relieved. Overall, these findings suggested that Trim14 may contribute to chronic inflammatory pain by degrading IκBα, and that Trim14 may become a novel therapeutic target for chronic inflammatory pain.

Chronic pain as an emergent property of a complex system and the potential roles of psychedelic therapies

Despite research advances and urgent calls by national and global health organizations, clinical outcomes for millions of people suffering with chronic pain remain poor. We suggest bringing the lens of complexity science to this problem, conceptualizing chronic pain as an emergent property of a complex biopsychosocial system. We frame pain-related physiology, neuroscience, developmental psychology, learning, and epigenetics as components and mini-systems that interact together and with changing socioenvironmental conditions, as an overarching complex system that gives rise to the emergent phenomenon of chronic pain. We postulate that the behavior of complex systems may help to explain persistence of chronic pain despite current treatments. From this perspective, chronic pain may benefit from therapies that can be both disruptive and adaptive at higher orders within the complex system. We explore psychedelic-assisted therapies and how these may overlap with and complement mindfulness-based approaches to this end. Both mindfulness and psychedelic therapies have been shown to have transdiagnostic value, due in part to disruptive effects on rigid cognitive, emotional, and behavioral patterns as well their ability to promote neuroplasticity. Psychedelic therapies may hold unique promise for the management of chronic pain.

A developmental framework for understanding the influence of sex and gender on health: Pediatric pain as an exemplar

Sex differences are a robust finding in many areas of adult health, including cardiovascular disease, psychiatric disorders, and chronic pain. However, many sex differences are not consistently observed until after the onset of puberty. This has led to the hypothesis that hormones are primary contributors to sex differences in health outcomes, largely ignoring the relative contributions of early developmental influences, emerging psychosocial factors, gender, and the interaction between these variables. In this paper, we argue that a comprehensive understanding of sex and gender contributions to health outcomes should start as early as conception and take an iterative biopsychosocial-developmental perspective that considers intersecting social positions. We present a conceptual framework, informed by a review of the literature in basic, clinical, and social science that captures how critical developmental stages for both sex and gender can affect children's health and longer-term outcomes. The literature on pediatric chronic pain is used as a worked example of how the framework can be applied to understanding different chronic conditions.

Familial effects account for association between chronic pain and past month smoking

BACKGROUND

Smoking is associated with chronic pain, but it is not established whether smoking causes pain or if the link is due to familial effects. One proposed mechanism is that smoking strengthens maladaptive cortico-striatal connectivity, which contributes to pain chronification. We leveraged a twin design to assess direct effects of smoking on pain controlling for familial confounds, and whether cortico-striatal connectivity mediates this association.

METHODS

In a population-based sample of 692 twins (age = 28.83 years), we assessed past-month smoking frequency (n = 132 used in the past month), presence and severity of a current pain episode (n = 179 yes), and resting-state functional connectivity of the nucleus accumbens and medial prefrontal cortex (NAc-mPFC).

RESULTS

Smoking was significantly associated with pain, but the association was not significantly mediated by NAc-mPFC connectivity. In a co-twin control model, smoking predicted which families had more pain but could not distinguish pain between family members. Pain risk was 43% due to additive genetic (A) and 57% due to non-shared environmental (E) influences. Past-month smoking frequency was 71% genetic and 29% non-shared environmental. Smoking and pain significantly correlated phenotypically (r = 0.21, p = 0.001) and genetically (rg  = 0.51, p < 0.001), but not environmentally (re  = -0.18, p = 0.339).

CONCLUSIONS

Pain and smoking are associated; however, the association appears to reflect shared familial risk factors, such as genetic risk, rather than being causal in nature. The connectivity strength of the reward pathway was not related to concurrent pain and smoking in this sample.

SIGNIFICANCE

Smoking does not appear to directly cause chronic pain; rather, there may be shared biopsychosocial risk factors, including genetic influences, that explain their association. These findings can be integrated into future research to identify shared biological pathways of both chronic pain and smoking behaviours as a way to conceptualize pain chronification.

The Prevalence of Anxiety Among Children in Saudi Arabia During the COVID-19 Pandemic: A Cross-Sectional Study

BACKGROUND

The year 2021 was a year that can be perceived as a stressful event given the considerable lifestyle changes that have occurred worldwide due to the pandemic. Several studies have investigated the psychological impact on people during this time period. However, only a few of them have investigated the impact on young children in Saudi Arabia (SA) specifically. Therefore, this study aimed to investigate the prevalence of anxiety in children living in Jeddah, Saudi Arabia.

METHODS

This is a cross-sectional study that included the parents of 388 children aged 6-9 years living in Jeddah, Saudi Arabia. It was conducted from June to November 2021. The parents completed an electronic survey that included the Arabic version of the Spence Children's Anxiety Scale. The data were analyzed using John's Macintosh Project (JMP) software version 10.0 (SAS Institute Inc., Cary, NC).

RESULTS

A total of 388 responses were collected. The data revealed that 37 (9.5%) participants experienced anxiety. Furthermore, the prevalence of anxiety was higher among females (5.15%) as compared to males (4.38%), but the difference was not statistically significant.

CONCLUSION

These findings highlight the importance of recognizing the psychological burden in young populations and emphasize the importance of taking children's well-being into account.

Enhanced harm detection following maternal separation: Transgenerational transmission and reversibility by inhaled amiloride

Early-life adversities are associated with altered defensive responses. Here, we demonstrate that the repeated cross-fostering (RCF) paradigm of early maternal separation is associated with enhancements of distinct homeostatic reactions: hyperventilation in response to hypercapnia and nociceptive sensitivity, among the first generation of RCF-exposed animals, as well as among two successive generations of their normally reared offspring, through matrilineal transmission. Parallel enhancements of acid-sensing ion channel 1 (ASIC1), ASIC2, and ASIC3 messenger RNA transcripts were detected transgenerationally in central neurons, in the medulla oblongata, and in periaqueductal gray matter of RCF-lineage animals. A single, nebulized dose of the ASIC-antagonist amiloride renormalized respiratory and nociceptive responsiveness across the entire RCF lineage. These findings reveal how, following an early-life adversity, a biological memory reducible to a molecular sensor unfolds, shaping adaptation mechanisms over three generations. Our findings are entwined with multiple correlates of human anxiety and pain conditions and suggest nebulized amiloride as a therapeutic avenue.

The Usefulness of the Short Form-8 for Chronic Pain in the Orofacial Region: A Prospective Cohort Study

Background and purpose Given that chronic pain has become a major problem in recent years, affecting approximately 30% of the general population, this study used the Japanese version of the Short Form-8 (SF-8) to investigate (1) the quality of life (QOL) of patients with burning mouth syndrome (BMS) or persistent idiopathic facial pain (PIFP) (compared with a Japanese control group) and (2) whether therapeutic intervention improves the QOL and reduces pain (comparison between 0 and 12 weeks) of patients with BMS or PIFP. Materials and methods A total of 63 patients diagnosed with either BMS (n=45) or PIFP (n=18) were included in this study. The diagnostic criteria for BMS and PIFP were established based on the third edition of the International Classification of Headache Disorders. Results Our study results showed that while Physical Component Summary (PCS) in patients with BMS or PIFP improved with treatment, it did not improve to the national standard value (NSV) after 12 weeks of intervention. In contrast, the Mental Component Summary (MCS) improved to the same level as the NSV after 12 weeks of intervention. Conclusions We found that therapeutic intervention improves MCS and reduces pain; however, improving PCS requires time.

Killing pain? A prospective population-based study on trauma exposure in childhood as predictor for frequent use of over-the-counter analgesics in young adulthood. The HUNT study

Frequent and increasing use of over-the-counter analgesics (OTCA) is a public health concern. Pain conditions and psychological distress are related to frequent OTCA use, and as exposure to potentially traumatic events (PTE) in childhood appears to increase risk of experiencing such symptoms, we aimed to assess childhood PTEs and related symptoms in adolescence as predictors for frequent OTCA use in young adulthood. Prospective population survey data were used (n = 2947, 59.1% female, 10-13 years follow-up). Exposure to PTEs, symptoms of post-traumatic stress, anxiety and depression, musculoskeletal pain and headache were assessed in adolescence (13-19 years). Use of OTCA was assessed in young adulthood (22-32 years) and use of OTCA to treat musculoskeletal pain and headache served as separate outcomes in ordinal logistic regression analyses. Overall, exposure to childhood PTEs, particularly direct interpersonal violence, was significantly and consistently related to more frequent use of OTCA to treat musculoskeletal pain and headaches in young adulthood. Adjusting for psychological symptoms and pain attenuated associations, indicating that these symptoms are of importance for the relationship between traumatic events and OTCA use. These findings emphasize the need to address symptomatology and underlying causes at an early age.

Associations Between Adolescent Pain and Psychopathology in the Adolescent Brain Cognitive Development (ABCD) Study

Pain and psychopathology co-occur in adolescence, but the directionality and etiology of these associations are unclear. Using the pain questionnaire and the Child Behavior Checklist from the Adolescent Brain Cognitive Development study (n = 10,414 children [770 twin pairs] aged 12-13), we estimated longitudinal, co-twin control, and twin models to evaluate the nature of these associations. In two-wave cross-lag panel models, there were small cross-lag effects that suggested bidirectional associations. However, the co-twin control models suggested that most associations were familial. Pain at age 12 and 13 was mostly environmental (A = 0-12%, C = 15-30%, E = 70-73%) and the twin models suggested that associations with psychopathology were primarily due to shared environmental correlations. The exception was externalizing, which had a phenotypic prospective effect on pain, a significant within-family component, and a non-shared environmental correlation at age 12. Environmental risk factors may play a role in pain-psychopathology co-occurrence. Future studies can examine risk factors such as stressful life events.

We need to talk: The urgent conversation on chronic pain, mental health, prescribing patterns and the opioid crisis

The opioid crisis’ pathways from first exposure onwards to eventual illnesses and fatalities are multiple, intertwined and difficult to dissect. Here, we offer a multidisciplinary appraisal of the relationships among mental health, chronic pain, prescribing patterns worldwide and the opioid crisis. Because the opioid crisis’ toll is especially harsh on young people, emphasis is given on data regarding the younger strata of the population. Because analgesic opioid prescription constitute a recognised entry point towards misuse, opioid use disorder, and ultimately overdose, prescribing patterns across different countries are examined as a modifiable hazard factor along these pathways of risk. Psychiatrists are called to play a more compelling role in this urgent conversation, as they are uniquely placed to provide synthesis and lead action among the different fields of knowledge and care that lie at the crossroads of the opioid crisis. Psychiatrists are also ideally positioned to gauge and disseminate the foundations for diagnosis and clinical management of mental conditions associated with chronic pain, including the identification of hazardous and protective factors. It is our hope to spark more interdisciplinary exchanges and encourage psychiatrists worldwide to become leaders in an urgent conversation with interlocutors from the clinical and basic sciences, policy makers and stakeholders including clients and their families.

Back Pain without Disease or Substantial Injury in Children and Adolescents: A Twin Family Study Investigating Genetic Influence and Associations

This twin family study first aimed to investigate the evidence for genetic factors predicting the risk of lifetime prevalence of non-specific low back pain of at least three months duration (LBP (life)) and one-month current prevalence of thoracolumbar back pain (TLBP (current)) using a study of children, adolescents, and their first-degree relatives. Secondly, the study aimed to identify associations between pain in the back with pain in other regions and also with other conditions of interest. Randomly selected families (n = 2479) with child or adolescent twin pairs and their biological parents and first siblings were approached by Twins Research Australia. There were 651 complete twin pairs aged 6-20 years (response 26%). Casewise concordance, correlation, and odds ratios were compared for monozygous (MZ) and dizygous (DZ) pairs to enable inference about the potential existence of genetic vulnerability. Multivariable random effects logistic regression was used to estimate associations between LBP (life) or TLBP (current) as an outcome with the potentially relevant condition as predictors. The MZ pairs were more similar than the DZ pairs for each of the back pain conditions (all p values < 0.02). Both back pain conditions were associated with pain in multiple sites and with primary pain and other conditions using the combined twin and sibling sample (n = 1382). Data were consistent with the existence of genetic influences on the pain measures under the equal environments assumption of the classic twin model and associations with both categories of back pain were consistent with primary pain conditions and syndromes of childhood and adolescence which has research and clinical implications.

Adolescent anxiety and pain problems: A joint, genome-wide investigation and pathway-based analysis

Both common pain and anxiety problems are widespread, debilitating and often begin in childhood-adolescence. Twin studies indicate that this co-occurrence is likely due to shared elements of risk, rather than reciprocal causation. A joint genome-wide investigation and pathway/network-based analysis of adolescent anxiety and pain problems can identify genetic pathways that subserve shared etiopathogenetic mechanisms. Pathway-based analyses were performed in the independent samples of: The Quebec Newborn Twin Study (QNTS; 246 twin pairs and 321 parents), the Longitudinal Study of Child Development in Quebec (QLSCD; n = 754), and in the combined QNTS and QLSCD sample. Multiple suggestive associations (p<1×10-5), and several enriched pathways were found after FDR correction for both phenotypes in the QNTS; many nominally-significant enriched pathways overlapped between pain problems and anxiety symptoms (uncorrected p<0.05) and yielded results consistent with previous studies of pain or anxiety. The QLSCD and the combined QNTS and QLSCD sample yielded similar findings. We replicated an association between the pathway involved in the regulation of myotube differentiation (GO:0010830) and both pain and anxiety problems in the QLSDC and the combined QNTS and QLSCD sample. Although limited by sample size and thus power, these data provide an initial support to conjoint molecular investigations of adolescent pain and anxiety problems. Understanding the etiology underlying pain and anxiety co-occurrence in this age range is relevant to address the nature of comorbidity and its developmental pathways, and shape intervention. The replication across samples implies that these effects are reliable and possess external validity.

Comparison of the Differences in State-Trait Anxiety Inventory Scores and Insomnia Histories between Monozygotic and Dizygotic Twins: A Cross-Sectional Study Using KoGES HTS Data

The heritability of anxiety and its association with insomnia have been suggested. This study investigated the coincidence of anxiety and insomnia in monozygotic twins compared to dizygotic twins. The Korean Genome and Epidemiology Study 2005–2014 was used. The ≥20-year-old cohort population was composed of 1300 twin participants. A total of 980 monozygotic twins and 232 dizygotic twins were compared for the concordance for the history of insomnia in both twin pairs (coincidence of insomnia) and the difference in state of anxiety and trait of anxiety scores. The odds ratios (ORs) for the coincidence of insomnia in monozygotic twins compared to dizygotic twins were analyzed using multiple logistic regression analysis. The estimated values (EV) of the difference of state and trait of anxiety scores were analyzed using a linear regression model. The coincidence of insomnia was not high in monozygotic twins compared to dizygotic twins. The difference in the state of anxiety score was comparable between monozygotic twins and dizygotic twins. However, the difference in anxiety scores was higher in dizygotic twins than in monozygotic twins. The monozygotic twin group did not demonstrate higher coincidence of insomnia or the state of anxiety than the dizygotic twin group. However, the monozygotic twin group indicated higher coincidence of the trait of anxiety than the dizygotic twins. The current results implied the potential contribution of heritable factors for the trait of anxiety.

Comorbidity and familial aggregation of back/neck pain in the NIMH Family Study of Affective Spectrum Disorders

OBJECTIVE

Back pain is associated with substantial Global Burden of Disease and is highly comorbid with mood and anxiety symptoms and syndromes. However, mechanisms underlying this association have not been well-elucidated. Here we apply data from the NIMH Family Study of Affective Spectrum Disorders to investigate the comorbidity, familial aggregation, and cross-aggregation of back/neck pain with mood disorder subtypes.

METHODS

The sample includes 519 probands and 560 interviewed first-degree relatives. Lifetime DSM-IV Bipolar I, Bipolar II, and Major Depressive Disorder [MDD] were derived from semi-structured diagnostic interviews. Lifetime history of back or neck pain and its age of onset were self-reported retrospectively. Familial aggregation and cross-aggregation were estimated via mixed effects models in probands and interviewed first-degree relatives, while heritability and co-heritability (endophenotypic ranking value [ERV]) were estimated using full pedigrees.

RESULTS

Over 45% of participants endorsed a history of back/neck pain. Back/neck pain was familial (adjusted odds ratio [aOR] 1.5, p = 0.04; h2 = 0.24, p = 0.009). Back/neck pain in probands was associated with MDD in relatives (aOR 1.5, p = 0.04; ERV = 0.17, p = 0.024), but not with bipolar disorder. Onset of back/neck pain occurred earlier in those with bipolar disorder compared to controls.

CONCLUSION

Findings suggest common familial risk factors underlying back/neck pain with MDD, whereas there was within-individual comorbidity of bipolar with back/neck pain. Future studies that identify common factors that lead to either back/neck pain or MDD can inform prevention and interventions.

The aetiological relationship between depressive symptoms and health-related quality of life: A population-based twin study in Sri Lanka

Objective

Depression often co-occurs with poor health-related quality of life (HRQL). Twin studies report genetic and individual-level environmental underpinnings in the aetiology of both depression and HRQL, but there is limited twin research exploring this association further. There is also little evidence on sex differences and non-Western populations are underrepresented. In this paper we explored the phenotypic and aetiological relationship between depressive symptoms and HRQL and possible sex differences in a low-middle-income Sri Lankan population.

Method

Data for 3,948 participants came from the Colombo Twin and Singleton Follow-up Study (CoTaSS-2). Using self-report measures of depressive symptoms and HRQL, we conducted univariate and bivariate sex-limitation twin analyses.

Results

Depressive symptoms showed moderate genetic (33%) and strong nonshared environmental influences (67%). Nonshared environment accounted for the majority of variance in all the subscales of HRQL (ranging from 68 to 93%), alongside small genetic influences (ranging from 0 to 23%) and shared environmental influences (ranging from 0 to 28%). Genetic influences were significant for emotional wellbeing (23%). Shared environmental influences were significant for four out of the eight HRQL variables (ranging from 22–28%), and they were more prominent in females than males. Depressive symptoms were significantly associated with lower HRQL scores. These correlations were mostly explained by overlapping nonshared environmental effects. For traits related to emotional functioning, we also detected substantial overlapping genetic influences with depressive symptoms.

Conclusions

Our study confirmed previous findings of a negative association between depressive symptoms and HRQL. However, some of the aetiological factors of HRQL differed from Western studies, particularly regarding the effects of shared environment. Our findings highlight the importance of cross-cultural research in understanding associations between psychological wellbeing and HRQL.

Adolescent pain, anxiety, and depressive problems: a twin study of their co-occurrence and the relationship to substance use

ABSTRACT

Data on the etiological factors underlying the co-occurrence of common adolescent pain with anxiety and depression symptoms are very limited. Opioid prescriptions for adolescent pain problems are on the rise in North America and constitute a risk factor for diversion, misuse, and substance use. In this study, we aimed to investigate the phenotypic and etiological association among pain, depression, and anxiety and to test their link to substance use in adolescents. By taking advantage of the Italian National Twin Registry and of the relatively low incidence of opioid prescriptions in Italy, we applied multivariate modelling analyses to 748 Italian adolescent twins (374 pairs, mean age 16 ± 1.24 years). Twins' responses to the Achenbach Youth Self-Report questionnaire were used to build a composite adolescent pain index and to measure anxiety, depression, and substance use. All monozygotic within-pair correlations were higher than the dizygotic correlations, indicating genetic influences for adolescent pain, anxiety, and depressive problems. A common latent liability factor influenced by genetic and environmental elements shared among pain, depression, and anxiety provided the best fit to explain the co-occurrence of adolescent pain, anxiety, and depression problems. A common phenotypic factor capturing all 3 phenotypes was positively associated (β = 0.19, P < 0.001, confidence interval: 0.10-0.27) with substance use. These findings indicate that several intertwined mechanisms, including genetic factors, can explain a shared liability to common adolescent pain, anxiety, and depression problems. Their association with substance use remains traceable even in societies with relatively low prevalence of opioid prescriptions.

Validity and utility of Hierarchical Taxonomy of Psychopathology (HiTOP): III. Emotional dysfunction superspectrum

The Hierarchical Taxonomy of Psychopathology (HiTOP) is a quantitative nosological system that addresses shortcomings of traditional mental disorder diagnoses, including arbitrary boundaries between psychopathology and normality, frequent disorder co-occurrence, substantial heterogeneity within disorders, and diagnostic unreliability over time and across clinicians. This paper reviews evidence on the validity and utility of the internalizing and somatoform spectra of HiTOP, which together provide support for an emotional dysfunction superspectrum. These spectra are composed of homogeneous symptom and maladaptive trait dimensions currently subsumed within multiple diagnostic classes, including depressive, anxiety, trauma-related, eating, bipolar, and somatic symptom disorders, as well as sexual dysfunction and aspects of personality disorders. Dimensions falling within the emotional dysfunction superspectrum are broadly linked to individual differences in negative affect/neuroticism. Extensive evidence establishes that dimensions falling within the superspectrum share genetic diatheses, environmental risk factors, cognitive and affective difficulties, neural substrates and biomarkers, childhood temperamental antecedents, and treatment response. The structure of these validators mirrors the quantitative structure of the superspectrum, with some correlates more specific to internalizing or somatoform conditions, and others common to both, thereby underlining the hierarchical structure of the domain. Compared to traditional diagnoses, the internalizing and somatoform spectra demonstrated substantially improved utility: greater reliability, larger explanatory and predictive power, and greater clinical applicability. Validated measures are currently available to implement the HiTOP system in practice, which can make diagnostic classification more useful, both in research and in the clinic.

Genetic basis to structural grey matter associations with chronic pain

Structural neuroimaging studies of individuals with chronic pain conditions have often observed decreased regional grey matter at a phenotypic level. However, it is not known if this association can be attributed to genetic factors. Here we employed a novel integrative data-driven and hypothesis-testing approach to determine whether there is a genetic basis to grey matter morphology differences in chronic pain. Using publicly available genome-wide association study summary statistics for regional chronic pain conditions (n = 196 963) and structural neuroimaging measures (n = 19 629-34 000), we applied bivariate linkage disequilibrium-score regression and latent causal variable analyses to determine the genetic correlations (rG) and genetic causal proportion (GCP) between these complex traits, respectively. Five a priori brain regions (i.e. prefrontal cortex, cingulate cortex, insula, thalamus and superior temporal gyrus) were selected based on systematic reviews of grey matter morphology studies in chronic pain. Across this evidence-based selection of five brain regions, 10 significant negative genetic correlations (out of 369) were found (false discovery rate < 5%), suggesting a shared genetic basis to both reduced regional grey matter morphology and the presence of chronic pain. Specifically, negative genetic correlations were observed between reduced insula grey matter morphology and chronic pain in the abdomen (mean insula cortical thickness), hips (left insula volume) and neck/shoulders (left and right insula volume). Similarly, a shared genetic basis was found for reduced posterior cingulate cortex volume in chronic pain of the hip (left and right posterior cingulate), neck/shoulder (left posterior cingulate) and chronic pain at any site (left posterior cingulate); and for reduced pars triangularis volume in chronic neck/shoulder (left pars triangularis) and widespread pain (right pars triangularis). Across these negative genetic correlations, a significant genetic causal proportion was only found between mean insula thickness and chronic abdominal pain [rG (standard error, SE) = -0.25 (0.08), P = 1.06 × 10-3; GCP (SE) = -0.69 (0.20), P = 4.96 × 10-4]. This finding suggests that the genes underlying reduced cortical thickness of the insula causally contribute to an increased risk of chronic abdominal pain. Altogether, these results provide independent corroborating evidence for observational reports of decreased grey matter of particular brain regions in chronic pain. Further, we show for the first time that this association is mediated (in part) by genetic factors. These novel findings warrant further investigation into the neurogenetic pathways that underlie the development and prolongation of chronic pain conditions.

Adolescent pain: appraisal of the construct and trajectory prediction-by-symptom between age 12 and 17 years in a Canadian twin birth cohort

ABSTRACT

Adolescent pain is common and continues into adulthood, leading to negative long-term outcomes including substance-related morbidity: an empirical definition of its construct may inform the early detection of persistent pain trajectories. These secondary analyses of a classical twin study assessed whether: headaches, back pains, abdominal pain, chest pains, stabbing/throbbing pain, gastric pain/nausea, measured in 501 pairs across 5 waves between age 12-17, fit a unitary construct, or constitute independent manifestations. We then assessed which symptoms were associated with a steady, 'frequent pain' trajectory that is associated with risk for early opioid prescriptions. Item Response Theory results indicated that all 6 pain symptoms index a unitary construct. Binary logistic regressions identified 'back pain' as the only symptom consistently associated with membership in the 'frequent adolescent pain' trajectory (OR:1.66-3.38) at all 5 measurement waves. Receiver Operating Characteristic analyses computed the discriminating power of symptoms to determine participants' membership into the 'frequent' trajectory: they yielded acceptable (.7-.8) to excellent (.8-.9) area under the curve (AUC) values for all 6 symptoms. The highest AUC was attained by 'back pain' at age 14 (.835); for multiple cut-off thresholds of symptom frequency, 'back pain' showed good sensitivity/false alarm probability trade-offs, predominantly in the 13-14-15 age range, to predict the 'frequent pain' trajectory. These data support a unitary conceptualization and assessment of adolescent pain, which is advantageous for epidemiological, clinical, and translational purposes. Persistent back pain constitutes a sensitive indicator of a steady trajectory of adolescent pain.

Electroacupuncture Attenuates Neuropathic Pain and Comorbid Negative Behavior: The Involvement of the Dopamine System in the Amygdala

Neuropathic pain (NeuP) is an important clinical problem accompanying negative mood symptoms. Neuroinflammation in the amygdala is critically involved in NeuP, and the dopamine (DA) system acts as an important endogenous anti-inflammatory pathway. Electroacupuncture (EA) can improve the clinical outcomes in NeuP, but the underlying mechanisms have not been fully elucidated. This study was designed to assess the effectiveness of EA on pain and pain-related depressive-like and anxiety-like behaviors and explore the role of the DA system in the effects of EA. Male Sprague-Dawley rats were subjected to the chronic constrictive injury (CCI) model to induce NeuP. EA treatment was carried out for 30 min once every other day for 3 weeks. The results showed that CCI caused mechanical hyperalgesia and depressive and anxiety-like behaviors in rats and neuroinflammation in the amygdala, such as an increased protein level of TNFα and IL-1β and activation of astrocytes. EA treatment significantly improved mechanical allodynia and the emotional dysfunction induced by CCI. The effects of EA were accompanied by markedly decreased expression of TNFα, IL-1β, and glial fibrillary acid protein (GFAP) in the amygdala. Moreover, EA treatment reversed CCI-induced down-regulation of DA concentration, tyrosine hydroxylase (TH) expression, and DRD1 and DRD2 receptors. These results suggest that EA-ameliorated NeuP may possibly be associated with the DA system to inhibit the neuroinflammation in the amygdala.

Factors associated with seeking medical care for low back pain in a twin adult sample

BACKGROUND

Previous studies have only investigated how symptom presentation and socio-demographic factors influence care-seeking for low back pain (LBP). However, the influence of health and lifestyle factors remains unclear, and the potential confounding effects of aggregated familial factors (including genetics and the early shared environment) has not been considered extensively.

METHODS

A cross-sectional analysis was performed on 1605 twins enrolled in the Murcia Twin Registry (Spain). The outcome was seeking medical care for LBP and various self-reported demographic, health and lifestyle factors were considered predictors. All variables except sleep quality and diabetes were collected in 2013, which were cross-referenced from 2009 to 2010. A multivariate logistic regression model was performed on the total sample, followed by a co-twin case-control analysis.

RESULTS

The only significant factor found to increase the odds of seeking medical care for LBP without being affected by familial factors was poor sleep quality (total sample OR = 1.58, 95%CI 1.24-2.01; case-control OR = 1.75, 95%CI 1.14-2.69). The factors that were associated with reduced odds of seeking medical care for LBP and not confounded by familial factors were male sex (case-control OR = 0.55, 95%CI 0.33-0.93), alcohol intake (case-control OR = 0.90, 95%CI 0.82-0.99) and a history of diabetes (case-control OR = 0.50, 95%CI 0.25-0.97). No other factors significantly influenced medical care-seeking for LBP.

CONCLUSIONS

People reporting poor sleep quality are more likely to seek medical care for LBP in the long term, with this relationship being independent from aggregated familial factors. Conversely, males, people reporting higher alcohol intake, and people with a history of diabetes are less likely to seek medical care for LBP.

SIGNIFICANCE

This is the first study investigating the factors that influence seeking medical care for LBP, while adjusting for the influence of familial factors using a co-twin control design. Poor sleep quality is associated with seeking medical care for LBP in the long term and does not appear to be confounded by familial factors. Early screening for indicators of poor sleep quality and appropriate referral to interventions for improving sleep quality or reducing pain in sleep may improve LBP management.

Functional pain disorders - more than nociplastic pain

BACKGROUND

Nociplastic pain has been recently introduced as a third mechanistic descriptor of pain arising primarily from alterations of neural processing, in contrast to pain due to tissue damage leading to nociceptor activation (nociceptive) or due to lesion or disease of the somatosensory nervous system (neuropathic). It is characterized by hyperalgesia and allodynia, inconsistency and reversibility, as well as dynamic cross-system interactions with biological and psychobehavioral factors. Along with this renewed understanding, functional pain disorders, also classified as chronic primary pain, are being reframed as biopsychosocial conditions that benefit from multimodal treatment.

OBJECTIVE

To summarize the current understanding of nociplastic pain and functional pain disorders, with a focus on conditions that are common in neurology practice.

METHODS

This was a narrative literature review.

RESULTS

Chronic back pain, fibromyalgia syndrome and complex regional pain syndrome are best understood within a biopsychosocial framework of pain perception that considers structural factors (predispositions and sequelae) and psychobehavioral mechanisms. Although pain is often the primary complaint, it should not be the only focus of treatment, as accompanying symptoms such as sleep or mood problems can significantly impact quality of life and offer useful leverage points for multimodal treatment. Analgesic pharmacotherapy is rarely helpful on its own, and should always be imbedded in a multidisciplinary setting.

Bromelain reduced pro-inflammatory mediators as a common pathway that mediate antinociceptive and anti-anxiety effects in sciatic nerve ligated Wistar rats

The involvement of pro-inflammatory mediators complicates the complex mechanism in neuropathic pain (NP). This study investigated the roles of bromelain against pro-inflammatory mediators as a mechanism that underpins its antinociceptive and anti-anxiety effects in the peripheral model of NP. Sixty-four male Wistar rats randomly divided into eight groups, were used for the study. A chronic constriction injury model of peripheral neuropathy was used to induce NP. Tail-immersion and von Frey filaments tests were used to assess hyperalgesia while open field and elevated plus mazes were used to assess anxiety-like behaviour. NF-кB, iNOS, nitrate, and pro-inflammatory cytokines were investigated in the plasma, sciatic nerve, and brain tissues using ELISA, spectrophotometer, and immunohistochemistry techniques after twenty-one days of treatment. Bromelain significantly (p < 0.05) improved the cardinal signs of NP and inhibited anxiety-like behaviours in ligated Wistar rats. It mitigated the increases in cerebral cortex interleukin (IL) -1β, IL-6, and PGE₂ levels. Bromelain reduced NF-кB, IL-1β, IL-6, TNF-α, PGE_2, and nitrate concentrations as well as the expression of iNOS in the sciatic nerve. Hence, the antinociceptive and anxiolytic effects of bromelain in the sciatic nerve ligation model of NP is in part due to its ability to reduce nitrosative and inflammatory activities.