Research highlights ► Pain evaluation is altered in IBS, irrespective of visceral pain thresholds. ► Negative emotions and expectations play an important role in pain evaluation. ► Pain processing in ...IBS is mediated by functional and structural brain changes. ► Peripheral neuroendocrine and immune pathways are also relevant in IBS. ► Studies on afferent immune-to-brain communication in visceral pain are needed.
Imaging of the living human brain is a powerful tool to probe the interactions between brain, gut and microbiome in health and in disorders of brain-gut interactions, in particular IBS. While altered ...signals from the viscera contribute to clinical symptoms, the brain integrates these interoceptive signals with emotional, cognitive and memory related inputs in a non-linear fashion to produce symptoms. Tremendous progress has occurred in the development of new imaging techniques that look at structural, functional and metabolic properties of brain regions and networks. Standardisation in image acquisition and advances in computational approaches has made it possible to study large data sets of imaging studies, identify network properties and integrate them with non-imaging data. These approaches are beginning to generate brain signatures in IBS that share some features with those obtained in other often overlapping chronic pain disorders such as urological pelvic pain syndromes and vulvodynia, suggesting shared mechanisms. Despite this progress, the identification of preclinical vulnerability factors and outcome predictors has been slow. To overcome current obstacles, the creation of consortia and the generation of standardised multisite repositories for brain imaging and metadata from multisite studies are required.
The role of psychological factors in the pathophysiology and treatment of chronic visceral pain in disorders of gut-brain interactions (DGBI) is increasingly appreciated. Placebo research has ...underscored that expectations arising from the psychosocial treatment context and from prior experiences shape treatment responses. However, effects of negative expectations, i.e., nocebo effects, as they are likely crucial elements of DGBI patients’ clinical reality, have thus far only rarely been investigated in the context of visceral pain, with untapped potential for improved prevention and treatment. The experimental randomized-controlled pain study “NoVis,” carried out within the Collaborative Research Center (CRC) 289 (“Treatment Expectation”), aims to close gaps regarding the generation and persistence of nocebo effects in healthy volunteers. It is designed to elucidate effects of negative expectations in a multiple-threat paradigm with intensity-matched rectal distensions and cutaneous thermal stimuli, allowing to test nocebo effects in the visceral and somatic pain modalities. Negative expectations are experimentally induced by elements of doctor-patient communication (i.e., instruction) and/or by surreptitious amplification of symptom intensity (i.e., experience/learning) within a treatment context. Accordingly, the repeated measures between-subject design contains the between-group factors “treatment instruction” (negative vs. control) and “treatment experience” (negative vs. control), with volunteers randomized into four experimental groups undergoing several pain stimulation phases (repeated factor). This allows to compare the efficacy of instruction vs. experience, and more importantly, their combined effects on the magnitude of negative expectations and their impact on pain responses, which we expect will be greatest for the visceral modality. After a
Baseline
, short-term effects are assessed during a test phase accomplished on study day 1 (
Test-1 Phase
). To explore the persistence of effects, a second test phase is accomplished 1 week later (
Test-2 Phase
). Effects of negative expectations within and across pain modalities are assessed at the subjective and objective levels, with a focus on psychophysiological and neuroendocrine measures related to stress, fear, and anxiety. Since nocebo effects can play a considerable role in the generation, maintenance, or worsening of chronic visceral pain, and may even constitute risk factors for treatment failure, knowledge from experimental nocebo research has potential to improve treatment outcomes in DGBI and other clinical conditions associated with chronic visceral pain.
Pain is evolutionarily hardwired to signal potential danger and threat. It has been proposed that altered pain-related associative learning processes, i.e., emotional or fear conditioning, might ...contribute to the development and maintenance of chronic pain. Pain in or near the face plays a special role in pain perception and processing, especially with regard to increased pain-related fear and unpleasantness. However, differences in pain-related learning mechanisms between the face and other body parts have not yet been investigated. Here, we examined body-site specific differences in associative emotional conditioning using electrical stimuli applied to the face and the hand. Acquisition, extinction, and reinstatement of cue-pain associations were assessed in a 2-day emotional conditioning paradigm using a within-subject design. Data of 34 healthy subjects revealed higher fear of face pain as compared to hand pain. During acquisition, face pain (as compared to hand pain) led to a steeper increase in pain-related negative emotions in response to conditioned stimuli (CS) as assessed using valence ratings. While no significant differences between both conditions were observed during the extinction phase, a reinstatement effect for face but not for hand pain was revealed on the descriptive level and contingency awareness was higher for face pain compared to hand pain. Our results indicate a stronger propensity to acquire cue-pain-associations for face compared to hand pain, which might also be reinstated more easily. These differences in learning and resultant pain-related emotions might play an important role in the chronification and high prevalence of chronic facial pain and stress the evolutionary significance of pain in the head and face.
More than eighty years after Hans Selye (1907-1982) first developed a concept describing how different types of environmental stressors affect physiological functions and promote disease development ...(called the "general adaptation syndrome") in 1936, we herein review advances in theoretical, mechanistic, and clinical knowledge in stress research, especially in the area of gastroenterology, and summarize progress and future perspectives arising from an interdisciplinary psychoneurobiological framework in which genetics, epigenetics, and other advanced (
omics) technologies in the last decade continue to refine knowledge about how stress affects the brain-gut axis in health and gastrointestinal disease. We demonstrate that neurobiological stress research continues to be a driving force for scientific progress in gastroenterology and related clinical areas, inspiring translational research from animal models to clinical applications, while highlighting some areas that remain incompletely understood, such as the roles of sex/gender and gut microbiota in health and disease. Future directions of research should include not only the genetics of the stress response and resilience but also epigenetic contributions.
Adverse side effects are reported by a large proportion of patients undergoing medical treatment in clinical practice or clinical trials. Nocebo effects, induced by negative treatment expectancies, ...can contribute to negative patient-reported outcomes but have rarely been studied in the context of inflammatory or immune-related conditions. Based on perceived treatment allocation, we herein analyzed nocebo responders in the placebo arms of randomized controlled double-blind experimental endotoxemia studies. We hypothesized that nocebo responders would report more bodily sickness symptoms and greater mood impairment. Out of
= 106 participants who had all received placebo injection,
= 20 (18.9%) wrongly believed they had received endotoxin and were thus considered as nocebo responders. Nocebo responders reported significantly more bodily sickness symptoms, suggesting that the perception of bodily symptoms affected perceived treatment allocation. Against our expectations, we did not find differences between nocebo responders and controls in psychological or physiological parameters. However, exploratory correlational analysis within nocebo responders revealed that more pronounced bodily sickness symptoms in response to placebo were associated with greater state anxiety and negative mood, as well as with the psychological traits catastrophizing and neuroticism. Our findings support that negative affectivity and personality-related factors may contribute to the reporting of sickness symptoms. Nonspecific symptoms experienced by patients undergoing pharmacological treatments or in randomized controlled trials can be misinterpreted and/or misattributed as unwanted side effects affecting perceived treatment allocation and presumably treatment satisfaction or its perceived efficacy. More nocebo research in the context of acute and chronic inflammatory conditions is warranted.
The aim of this study was to compare the performance of fecal lactoferrin (Lf), calprotectin (Cal), polymorphonuclear neutrophil elastase (PMN-e), as well as serum C-reactive protein (CRP) in ...patients with inflammatory bowel diseases (IBD) to address (a) whether these markers can differentiate IBD patients with endoscopically assessed inflammation from IBD patients without inflammation and from irritable bowel syndrome (IBS); (b) whether they correlate with endoscopic severity of inflammation; and (c) whether a combination of fecal markers with the respective disease-specific activity indices may increase the diagnostic accuracy with reference to the endoscopic severity of inflammation.
Fecal levels of Lf, Cal, and PMN-e and serum CRP were assessed in 139 patients undergoing diagnostic ileocolonoscopy (54 IBS patients, 42 ulcerative colitis UC, 43 Crohn's disease CD). Disease activity was determined for CU with the colitis activity index (CAI) and for CD with the Crohn's disease activity index (CDAI). The performance of each marker with reference to endoscopic inflammatory activity was assessed by computing correlations, and sensitivity and specificity using published as well as adjusted cutoffs. A comprehensive activity index was computed by combining results from fecal markers, serum CRP, and a clinical activity index.
UC or CD patients with active inflammation demonstrated significantly higher levels of Lf, Cal, and PMN-e in feces as well as serum-CRP when compared to patients with inactive inflammation as well as patients with IBS (all P < 0.05). Using adjusted cutoffs enabled a marked improvement of all markers with an overall diagnostic accuracy in IBD of 80.0% for Lf, 80.0% for Cal, 74.1% for PMN-e, 64.0% for CRP, and 79.0% for the respective clinical disease scores. Cal showed the highest diagnostic accuracy in CD (81.4%), whereas Lf was superior to the other markers in UC (83.3%). The comprehensive activity index yielded a further improvement of sensitivity and specificity, with a diagnostic accuracy of 95.3% for UC patients.
The fecal markers Lf, Cal, and PMN-e are able to differentiate active IBD from inactive IBD as well as from IBS. None of these three stool markers is consistently superior in its ability to reflect endoscopic inflammation, but all three are superior to CRP in their diagnostic accuracy. A combination of the stool markers with the CRP and a disease-specific activity index in a categorical comprehensive activity index can increase the diagnostic accuracy with reference to the endoscopic inflammation in UC.
The brain systems underlying placebo analgesia are insufficiently understood. Here we performed a systematic, participant-level meta-analysis of experimental functional neuroimaging studies of evoked ...pain under stimulus-intensity-matched placebo and control conditions, encompassing 603 healthy participants from 20 (out of 28 eligible) studies. We find that placebo vs. control treatments induce small, widespread reductions in pain-related activity, particularly in regions belonging to ventral attention (including mid-insula) and somatomotor networks (including posterior insula). Behavioral placebo analgesia correlates with reduced pain-related activity in these networks and the thalamus, habenula, mid-cingulate, and supplementary motor area. Placebo-associated activity increases occur mainly in frontoparietal regions, with high between-study heterogeneity. We conclude that placebo treatments affect pain-related activity in multiple brain areas, which may reflect changes in nociception and/or other affective and decision-making processes surrounding pain. Between-study heterogeneity suggests that placebo analgesia is a multi-faceted phenomenon involving multiple cerebral mechanisms that differ across studies.
Highlights • LPS administration is well-established to assess behavioral aspects of inflammation. • We analyzed predictors of LPS-induced state anxiety in a large pooled sample. • LPS-induced state ...anxiety increase was predicted by greater cytokine responses. • Pre-existing anxiety symptoms predicted a lower increase in state anxiety. • Our findings support a role of inflammation in the pathophysiology of anxiety.
This functional magnetic resonance imaging study addressed similarities and differences in behavioral and neural responses to experimental visceral compared with somatic pain stimuli and explored the ...contribution of fear of pain to differences between pain modalities. In N = 22 healthy women, we assessed blood oxygen level-dependent responses to rectal distensions and cutaneous heat stimuli matched for perceived pain intensity. Fear of pain and pain unpleasantness were assessed before and after scanning. Visceral pain was more fear evoking and more unpleasant, and trial-by-trial intensity ratings failed to habituate across trials (all interactions modality × time: P < 0.01). Differences in fear of pain and pain intensity independently contributed to greater visceral pain unpleasantness (combined regression model: R(2) = 0.59). We observed joint neural activations in somatosensory cortex and frontoparietal attention network (conjunction analysis: all pFWE <0.05), but distensions induced greater activation in somatosensory cortex, dorsal and ventral anterior insula, dorsal anterior and midcingulate cortices, and brainstem, whereas cutaneous heat pain led to enhanced activation in posterior insula and hippocampus (all pFWE <0.05). Fear of visceral pain correlated with prefrontal activation, but did not consistently contribute to neural differences between modalities. These findings in healthy women support marked differences between phasic pain induced by rectal distensions vs cutaneous heat, likely reflecting the higher salience of visceral pain. More studies with clinically relevant pain models are needed to discern the role of fear in normal interindividual differences in the response to different types of pain and as a putative risk factor in the transition from acute to chronic pain.
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