Five-factor personality traits and pain sensitivity: a twin study

Are you ready for a challenge? Personality traits influence dairy calves' responses to disease, pain, and nutritional challenges

Dairy calves routinely experience disease, pain, and nutritional stressors such as diarrhea, dehorning, and weaning early in life. These stressors lead to changes in behavioral expression that varies in magnitude between individuals, where a greater magnitude change would suggest lower resilience in individuals to a stressor. Thus, this study first aimed to quantify the individual variation in magnitude change in feeding behaviors and activity in response to a bout of diarrhea, dehorning, and weaning. The next objective was to then investigate if personality traits were related to this magnitude of behavioral response in dairy calves, and thus their resilience toward these stressors. Calves were followed with 2 precision livestock technologies (e.g., an automatic feeding system, and leg accelerometer) to track behavioral changes in response during the time when the stressors were present. The automatic feeding system provided daily measures of milk intake, drinking speed, rewarded and unrewarded visits to the milk feeding station, and calf starter intake. The leg accelerometer provided daily measures of steps, activity index, lying time, and lying bouts. At 23 ± 3 d of age, Holstein dairy calves (n = 49) were subjected to a series of standardized personality tests that exposed the calf to novelty and fear stimuli. Factors extracted from a principal component analysis on the behaviors from the personality test were interpreted as personality traits: Factor 1 (fearful), Factor 2 (active) and Factor 3 (explorative). The magnitude changes in behaviors from the precision livestock technologies were calculated relative to the behavior performed on the day the stressor occurred (i.e., day of diagnosis, day of dehorning, day weaned). Linear regression models were used to determine whether calf scores on each factor were associated with magnitude change in behavior for each of the stressor periods with day relative to the stressor included as a repeated measure. Models were run independently for the period leading up to and following each stressor. We found that calves varied in their behavioral responses to diarrhea, dehorning, and weaning stressors, despite being reared in the same environment and experiencing consistent management procedures. Additionally, personality traits measured from standardized tests were associated with both the direction and magnitude of change in behaviors around each stressor. For instance, with diarrhea, calves that were highly fearful had a greater magnitude change in milk intake and drinking speed following diagnosis than the least fearful calves. With dehorning, calves that were highly explorative had a greater magnitude change in lying time when dehorned, but a smaller magnitude change in lying bouts and drinking speed following dehorning, compared with the least explorative calves. With weaning, calves that were highly active had a smaller magnitude change in unrewarded visits leading up to and following weaning than calves that were the least active. Each of the personality traits had a significant association with change in behavior surrounding each of the stressors evaluated, although these associations depended on the type of stressor. These results have implications for how individual calves experience each stressor and therefore individual animal welfare.

Unpacking the relationship between Big Five personality traits and experimental pain: A systematic review and meta-analysis

Pain is essential for survival, but individual responses to painful stimuli vary, representing a complex interplay between sensory, cognitive, and affective factors. Individual differences in personality traits and in pain perception covary but it is unclear which traits play the most significant role in understanding the pain experience and whether this depends on pain modality. A systematic search identified 1534 records (CINAHL, MEDLINE, PsycInfo, PubMed and Web of Science), of which 22 were retained and included in a systematic review. Only studies from the pressure pain domain (n=6) could be compared in a formal meta-analysis to evaluate the relationship between Big Five traits and experimental pain. Pressure pain tolerance correlated positively with Extraversion and negatively with Neuroticism with a trivial effect size (<0.1). While these findings suggest personality might be only weakly related to pain in healthy individuals, we emphasize the need to consider standardization, biases, and adequate sample sizes in future research, as well as additional factors that might affect experimental pain sensitivity.

Validation and Cross-Cultural Adaptation of the Spanish Version of the Pain Sensitivity Questionnaire (PSQ-S)

Experimental pain testing requires specific equipment and may be uncomfortable for patients. The Pain Sensitivity Questionnaire (PSQ) was developed to assess pain sensitivity, based on the pain intensity ratings (range: 0–10) of painful situations that occur in daily life. The main objective of this study was to carry out a cross-cultural adaptation and validation of the Spanish version of the PSQ (PSQ-S). A total of 354 subjects (296 healthy and 58 chronic pain patients) filled in the PSQ-S. A subgroup of 116 subjects performed experimental pain testing, including two modalities (cold and pressure), with different measures: pain intensity rating, pressure pain threshold, and tolerance. The validation results showed two factors: PSQ-S-moderate and PSQ-S-minor and, for the total scale and the two factors, an excellent internal consistency (Cronbach’s alpha coefficient > 0.9) and a substantial reliability (Intraclass Correlation Coefficient > 0.8). We obtained strong correlations with all the experimental pain rating parameters, catastrophizing, and depression variables, as well as moderate correlations with anxiety, central sensibilization, and impact on the quality of life. Chronic pain patients received elevated PSQ-S scores compared to healthy controls, and three cut-off values (PSQ-S-total = 7.00, PSQ-S-moderate = 7.57, and PSQ-S-minor = 6.29) based on ROC curve analyses were shown to be able to discriminate between healthy adults and adults with chronic pain. Therefore, PSQ-S may be a simple alternative to experimental pain procedures for clinical and experimental pain research.

Personalized behavior management as a replacement for medications for pain control and mood regulation

A lack of personalized approaches in non-medication pain management has prevented these alternative forms of treatment from achieving the desired efficacy. One hundred and ten female patients with fibromyalgia syndrome (FMS) and 60 healthy women without chronic pain were assessed for severity of chronic or retrospective occasional pain, respectively, along with alexithymia, depression, anxiety, coping strategies, and personality traits. All analyses were conducted following a ‘resource matching’ hypothesis predicting that to be effective, a behavioral coping mechanism diverting or producing cognitive resources should correspond to particular mechanisms regulating pain severity in the patient. Moderated mediation analysis found that extraverts could effectively cope with chronic pain and avoid the use of medications for pain and mood management by lowering depressive symptoms through the use of distraction mechanism as a habitual (‘out-of-touch-with-reality’) behavior. However, introverts could effectively cope with chronic pain and avoid the use of medications by lowering catastrophizing through the use of distraction mechanism as a situational (‘in-touch-with-reality’) behavior. Thus, personalized behavior management techniques applied according to a mechanism of capturing or diverting the main individual ‘resource’ of the pain experience from its ‘feeding’ to supporting another activity may increase efficacy in the reduction of pain severity along with decreasing the need for pain relief and mood-stabilizing medications.

More Insight on the Role of Personality Traits and Sensitivity to Experimental Pain

Purpose

The present study aimed to assess the influence of personality traits on the variability of sensitivity to pain in two distinct groups of healthy subjects with low versus high sensitivity to pain (LSP vs HSP, respectively).

Methods

Healthy subjects (n=156) were allocated to two groups according to their tolerability to cold stimulation (cold pressor test, CPT, 1°C). Group LSP (n=76) reached the cut-off time of 180±0 sec, and a size matched group of HSP (n=80) tolerated the CPT for an average of 10.5±3.4 sec only. Subjects from both groups completed the self-reported pain sensitivity questionnaire (PSQ), the Pain Catastrophizing Scale (PCS), and the Neuroticism Extraversion Openness - Five Factor Inventory (NEO-FFI).

Results

In comparison to the LSP group, HSP individuals had higher scores of PSQ (p<0.001), catastrophizing (p=0.001), and extraversion (p=0.01). By adjusting for age and gender, mediation analyses revealed that catastrophizing mediated the relationship between neuroticism and pain sensitivity, both in the allocation of subjects to a certain group of sensitivity to pain (LSP or HSP, B=0.02 95% CI: 0.006–0.040) and in the PSQ score (B=0.01 95% CI: 0.001–0.023).

Conclusion

These results, which were demonstrated by two different prisms (CPT and PSQ), point to the potential of the five-factor inventory and pain catastrophizing scale as tools for identifying specific personality traits associated with a high sensitivity to pain.

Multi-sensory Responsiveness and Personality Traits Predict Daily Pain Sensitivity

Background: A continuous effort has been devoted to identifying factors that contribute to individual differences in pain perception. Amongst the personality traits, Neuroticism is assumed to be the most significant moderator of experimental and clinical pain. Multi-sensory responsiveness to daily sensations has been shown to be associated with pain perception. Yet, neither the relationship between personality traits and multi-sensory responsiveness nor the impact of both these factors to pain perception have been examined. Thus, this study aims to explore the contribution of both multi-sensory responsiveness and personality traits to pain perception in a daily context.

Methods: A community-based sample of 204 adults completed the Sensory Responsiveness Questionnaire-Intensity Scale (SRQ-IS); the Big Five Inventory (BFI); and the Pain Sensitivity Questionnaire (PSQ).

Results: The partial eta-square demonstrated that the SRQ-IS Aversive sub-scale score had the strongest relationship with the PSQ-Total score, accounting for 9% of the variation. The regression coefficient relating PSQ-Total score with SRQ-IS Aversive, and BFI sub-scales of Extraversion, Neuroticism and Openness-to-Experience scores was found to be r = 0.39 (p < 0.0001), accounting for 16% of the variance, and yielding a large effect size.

Discussion: To the best of our knowledge this is the first study to report on the interplay between aversive responsiveness to daily sensations and personality traits of Neuroticism, Openness-to-Experience, and Extraversion as contributing factors to daily pain sensitivity, amongst which aversive responsiveness was found as the major contributing factor. This study may broaden the understanding of the pain experience variability, both in practice and in experimental research.

Deep heating therapy via MF radiowaves versus superficial heating therapy in the treatment of nonspecific chronic low back pain: A double blind randomized trial

BACKGROUND

Nonspecific Chronic Low Back Pain (CLBP) is a condition difficult to treat due to multiple etiopathogenesis and there is wide consensus on the multidisciplinary approach. In physiotherapy, the Medium Frequencies (MF) diathermy has recently been introduced but without enough evidence of effectiveness.

OBJECTIVE

To explore the effects of a deep heating therapy (DHT) produced by a MF diathermy for the treatment of CLBP compared with a superficial heating therapy (SHT). The study was a double blind randomized trial.

METHODS

Forty-nine patients affected by CLBP were randomly subdivided in 2 groups and treated with either DHT (450 KHz) or SHT via electric resistance applying the same instrument on the lumbar spine. NRS (Numerical Rating Scale) for pain and ODI (Oswestry Disability Index) for disability were used as outcome measures. The follow up was: T1, 15 days (end of the therapy); T2, 30 days; T3, 45 days after T0.

RESULTS

Both therapies were effective in reducing pain throughout the follow up with greater improvement in DHT group at T1. DHT resulted to have a higher efficacy with respect to SHT in reducing disability (ODI) throughout all follow ups.

CONCLUSION

This study provides evidence of the positive effects of MF radio waves diathermy in the treatment of CLBP.

Neuroticism and pain catastrophizing aggravate response to pain in healthy adults: an experimental study

Background

The aim of this study was to investigate the association between neuroticism, pain catastrophizing, and experimentally induced pain threshold and pain tolerance in a healthy adult sample from two regions of the country of Croatia: the island of Korcula and city of Split.

Methods

A total of 1,322 participants were enrolled from the Island of Korcula (n = 824) and the city of Split (n = 498). Participants completed a self-reported personality measure Eysenck Personality Questionnaire (EPQ) and pain catastrophizing questionnaire Pain Catastrophizing Scale (PCS), followed by a mechanical pain pressure threshold and tolerance test. We have explored the mediating role of catastrophizing in the relationship between neuroticism and pain intensity.

Results

The results showed that pain catastrophizing partially mediated the relationship between neuroticism and pain intensity, suggesting the importance of pain catastrophizing in increasing vulnerability to pain. The results also indicated gender-related differences, marked by the higher pain threshold and tolerance in men.

Conclusions

This study adds to the understanding of the complex interplay between personality and pain, by providing a better understanding of such mechanisms in healthy adults.

Association between physical activity and pain processing in adults with chronic low back pain compared to pain-free controls

BACKGROUND

Pain sensitivity has been negatively associated with physical activity levels. Few studies have examined associations between experimentally induced pain sensitivity and physical activity in adults with chronic low back pain and pain-free controls.

OBJECTIVE

The objective of this study was to examine associations between physical activity levels and how an individual processes pain using experimentally induced pain stimuli.

METHODS

Seventy subjects (CLBP = 49; mean age = 46.8 ± 14.9; Pain-free = 21; mean age = 45.3 ± 18.2, n of females = 46) participated. A self-report questionnaire derived from the International Physical Activity Questionnaire (IPAQ) was used to calculate an activity level index. Pain sensitivity was assessed via quantitative sensory testing (QST) at the right lower extremity.

RESULTS

Moderate (U = 688, p< 0.05) and vigorous (U = 649, p< 0.05) physical activity levels were higher in pain-free vs. individuals with CLBP. Activity level was not associated with pain sensitivity (Pain-free: R2 = 0.02, p> 0.05; CLBP: R2 = 0.01, p> 0.05). Both moderate (R2 = 0.49, p< 0.05) and vigorous (R2 = 0.68, p< 0.01) physical activity were associated with pain modulation amongst pain-free individuals.

CONCLUSIONS

Findings suggest that physical activity influences pain modulation amongst pain-free individuals, however no relationship exists once CLBP is present. However, future investigation will elucidate the extent to which physical activity level either prevents CLBP or is effective in alleviating CLBP.

An Integrative Review of the Influence of Expectancies on Pain

Expectancies can shape pain experiences. Attention for the influence of expectancies on pain has increased particularly due to research on placebo effects, of which expectancy is believed to be the core mechanism. In the current review, we provide a brief overview of the literature on the influence of expectancies on pain. We first discuss the central role of expectancy in the major psychological learning theories. Based on these theories, different kinds of expectancies can be distinguished. Pain experiences are influenced particularly by response expectancies directly pertaining to the pain experience itself, but can also be affected by self-efficacy expectancies regarding one's ability to cope with pain, and possibly by stimulus expectancies regarding external events. These different kinds of expectancies might interact with each other, and related emotions and cognitions, as reflected by various multifaceted constructs in which expectancies are incorporated. Optimism and pain catastrophizing, in particular, but also hope, trust, worry, and neuroticism have been found to be associated with pain outcomes. We conclude with recommendations for further advancing research on the influence of expectancies on pain and for harnessing expectancy effects in clinical practice.

Risk factors associated with postoperative pain after ophthalmic surgery: a prospective study

BACKGROUND

Risk factors associated with postoperative pain intensity and duration, as well as consumption of analgesics after ophthalmic surgery are poorly understood.

METHODS

A prospective study was conducted among adults (N=226) who underwent eye surgery at the University Hospital Split, Croatia. A day before the surgery, the patients filled out questionnaires assessing personality, anxiety, pain catastrophizing, sociodemographics and were given details about the procedure, anesthesia, and analgesia for each postoperative day. All scales were previously used for the Croatian population. The intensity of pain was measured using a numerical rating scale from 0 to 10, where 0 was no pain and 10 was the worst imaginable pain. The intensity of pain was measured before the surgery and then 1 hour, 3 hours, 6 hours, and 24 hours after surgery, and then once a day until discharge from the hospital. Univariate and multivariate analyses were performed.

RESULTS

A multivariate analysis indicated that independent predictors of average pain intensity after the surgery were: absence of premedication before surgery, surgery in general anesthesia, higher pain intensity before surgery and pain catastrophizing level. Independent predictors of postoperative pain duration were intensity of pain before surgery, type of anesthesia, and self-assessment of health. Independent predictors of pain intensity ≥5 during the first 6 hours after the procedure were the type of procedure, self-assessment of health, premedication, and the level of pain catastrophizing.

CONCLUSION

Awareness about independent predictors associated with average postoperative pain intensity, postoperative pain duration, and occurrence of intensive pain after surgery may help health workers to improve postoperative pain management in ophthalmic surgery.

Extraversion modulates functional connectivity hubs of resting-state brain networks

Personality dimension extraversion describes individual differences in social behaviour and socio-emotional functioning. The intrinsic functional connectivity patterns of the brain are reportedly associated with extraversion. However, whether or not extraversion is associated with functional hubs warrants clarification. Functional hubs are involved in the rapid integration of neural processing, and their dysfunction contributes to the development of neuropsychiatric disorders. In this study, we employed the functional connectivity density (FCD) method for the first time to distinguish the energy-efficient hubs associated with extraversion. The resting-state functional magnetic resonance imaging data of 71 healthy subjects were used in the analysis. Short-range FCD was positively correlated with extraversion in the left cuneus, revealing a link between the local functional activity of this region and extraversion in risk-taking. Long-range FCD was negatively correlated with extraversion in the right superior frontal gyrus and the inferior frontal gyrus. Seed-based resting-state functional connectivity (RSFC) analyses revealed that a decreased long-range FCD in individuals with high extraversion scores showed a low long-range functional connectivity pattern between the medial and dorsolateral prefrontal cortex, middle temporal gyrus, and anterior cingulate cortex. This result suggests that decreased RSFC patterns are responsible for self-esteem, self-evaluation, and inhibitory behaviour system that account for the modulation and shaping of extraversion. Overall, our results emphasize specific brain hubs, and reveal long-range functional connections in relation to extraversion, thereby providing a neurobiological basis of extraversion.

Heritability of pain catastrophizing and associations with experimental pain outcomes: a twin study

This study used a twin paradigm to examine genetic and environmental contributions to pain catastrophizing and the observed association between pain catastrophizing and cold-pressor task (CPT) outcomes. Male and female monozygotic (n = 206) and dizygotic twins (n = 194) from the University of Washington Twin Registry completed a measure of pain catastrophizing and performed a CPT challenge. As expected, pain catastrophizing emerged as a significant predictor of several CPT outcomes, including cold-pressor Immersion Tolerance, Pain Tolerance, and Delayed Pain Rating. The heritability estimate for pain catastrophizing was found to be 37% with the remaining 63% of variance attributable to unique environmental influence. Additionally, the observed associations between pain catastrophizing and CPT outcomes were not found attributable to shared genetics or environmental exposure, which suggests a direct relationship between catastrophizing and experimental pain outcomes. This study is the first to examine the heritability of pain catastrophizing and potential processes by which pain catastrophizing is related to experimental pain response.

Personality subtypes and chest pain in patients with nonobstructive coronary artery disease from the TweeSteden Mild Stenosis study: mediating effect of anxiety and depression

BACKGROUND

Patients presenting with chest pain in nonobstructive coronary artery disease (CAD, luminal narrowing <60%) are at risk for emotional distress and future events. We aimed to examine the association of personality subtypes with persistent chest pain, and investigated the potential mediating effects of negative mood states.

METHODS

Any chest pain in the past month was the primary outcome measure reported by 523 patients with nonobstructive CAD (mean age 61.4 years, SD = 9.4; 48% men), who participate in the TweeSteden Mild Stenosis (TWIST) observational cohort. Personality was categorized into a 'reference group', a high social inhibition ('SI only'), a high negative affectivity ('NA only') and a 'Type D' (NA and SI) group. Negative mood states included symptoms of depression and anxiety (Hospital Anxiety and Depression Scale) and cognitive and somatic depression (Beck Depression Inventory). The PROCESS macro was used to examine the relation between personality subtypes and chest pain presence, with the negative mood states as potential mediators.

RESULTS

Persistent chest pain was present in 44% of the patients with nonobstructive CAD. Type D personality (OR = 1.91, 95% CI 1.24-2.95), but not the 'NA only' (OR = 1.48, 95% CI 0.89-2.44) or the 'SI only' (OR = 0.93, 95% CI 0.53-1.64) group was associated with chest pain, adjusted for age and sex. Negative mood states mediated the association between personality and chest pain.

CONCLUSIONS

Type D personality, but not negative affectivity or social inhibition, was related to chest pain in nonobstructive CAD, which was mediated by negative mood states.

The influence of personality traits on perception of pain in older adults – Findings from the Swedish National Study on Aging and Care – Blekinge study

Background and aims

The experience of pain may vary in accordance with personality traits and individual characteristics. Neuroticism is demonstrated to constitute a vulnerability factor among younger and middle-aged pain patients. The combination of openness and neuroticism is associated with high anxiety/depression scores among adult individuals with chronic conditions. The aim of this study was to investigate possible associations between pain and the personality dimensions of neuroticism, extroversion, openness, agreeableness and conscientiousness among persons aged 60 years and older. An additional aim was to explore whether such associations are equally gender expressed.

Methods

The Swedish National Study on Aging and Care includes a randomly selected sample from the National Population Register. The data collection was conducted at four research centres and was approved by the Ethics Committees of Lund University and the Karolinska Institutet, Stockholm, Sweden. The Blekinge sample includes 1402 individuals, aged 60–96 years, of whom 769 (55%) reported pain. A total of 2312 individuals had been invited to participate. The reason for non-participation was registered. Participants underwent medical examination and testing by research personnel, conducted in two sessions, each of which lasted about 3 h. A questionnaire was completed between the two sessions. Pain was self-reported and based on the question: Have you had ache/pain during the last 4 weeks? Information on personality traits was obtained by means of the personality SGC1 questionnaire; a 60-item Swedish version of Costa & McCrae’s FFM questionnaire. Personality traits were then tested based on gender by means of multivariate forward logistic regression in models adjusted for age, insomnia, financial status and educational level.

Results

When adjusting for covariates among women, neuroticism had a small but significant odds ratio of experiencing pain (OR 1.05, CI 1.02–1.08). Insomnia had the highest odds ratio (OR 2.19, CI 1.52–3.15) followed by low education (OR 1.59, CI 1.07–2.36), while belonging to the younger part of the older adult cohort was also associated with pain (OR 1.02, CI 1.005–1.04). In men, neuroticism (OR 1.03, CI 1.002–1.06) followed by openness (OR 1.03 CI 1.001–1.07) had a small but significant odds ratio of experiencing pain. Insomnia had the highest odds ratio (OR 1.98, CI 1.24–3.15).

Conclusions

Personality traits and pain were related among the older adults but there were gender differences. The relationship between pain and neuroticism in women was about the same in strength as the relation between pain and neuroticism/openness in men. Both sexes suffer from insomnia. The relationship between personality traits and pain was only affected to a minor extent by insomnia.

Implications

There is a need to increase awareness of the impact of personality as well as to provide improved treatment for pain and insomnia in older people.

Dynamic interactions between plasma IL-1 family cytokines and central endogenous opioid neurotransmitter function in humans

Evidence in animal models suggests IL-1 family cytokines interact with central endogenous opioid neurotransmitter systems, inducing or perpetuating pathological states such as persistent pain syndromes, depression, substance use disorders, and their comorbidity. Understanding these interactions in humans is particularly relevant to understanding pathological states wherein this neurotransmitter system is implicated (ie, persistent pain, mood disorders, substance use disorders, etc). Here, we examined relationships between IL-1β, IL-1ra, and functional measures of the endogenous opioid system in 34 healthy volunteers, in the absence and presence of a standardized sustained muscular pain challenge, a psychophysical challenge with emotionally and physically stressful components. Mu-opioid receptor availability in vivo was examined with [(11)C]carfentanil positron emission tomography (PET) scanning. Sex and neuroticism impacted IL-1 family cytokines; higher baseline IL-1β and IL-1ra was identified in females with lower neuroticism. Higher baseline IL-1β was also associated with reduced μ-opioid receptor availability (amygdala) and greater pain sensitivity. The pain challenge increased IL-1β in females with high neuroticism. Strong associations between IL-1ra (an anti-nociceptive cytokine) and μ-opioid receptor activation (VP/NAcc) were identified during the pain challenge and the resulting analgesic effect of μ-opioid receptor activation was moderated by changes in IL-1β whereby volunteers with greater pain induced increase in IL-1β experienced less endogenous opioid analgesia. This study demonstrates the presence of relationships between inflammatory factors and a specific central neurotransmitter system and circuitry, of relevance to understanding interindividual variations in regulation of responses to pain and other physical and emotional stressors.

Clinical and evoked pain, personality traits, and emotional states: can familial confounding explain the associations?

OBJECTIVES

Pain is a complex phenomenon influenced by context and person-specific factors. Affective dimensions of pain involve both enduring personality traits and fleeting emotional states. We examined how personality traits and emotional states are linked with clinical and evoked pain in a twin sample.

METHODS

99 female twin pairs were evaluated for clinical and evoked pain using the McGill Pain Questionnaire (MPQ) and dolorimetry, and completed the 120-item International Personality Item Pool (IPIP), the Positive and Negative Affect Scale (PANAS), and ratings of stress and mood. Using a co-twin control design we examined a) the relationship of personality traits and emotional states with clinical and evoked pain and b) whether genetics and common environment (i.e. familial factors) may account for the associations.

RESULTS

Neuroticism was associated with the sensory component of the MPQ; this relationship was not confounded by familial factors. None of the emotional state measures was associated with the MPQ. PANAS negative affect was associated with lower evoked pressure pain threshold and tolerance; these associations were confounded by familial factors. There were no associations between IPIP traits and evoked pain.

CONCLUSIONS

A relationship exists between neuroticism and clinical pain that is not confounded by familial factors. There is no similar relationship between negative emotional states and clinical pain. In contrast, the relationship between negative emotional states and evoked pain is strong while the relationship with enduring personality traits is weak. The relationship between negative emotional states and evoked pain appears to be non-causal and due to familial factors.

Functional brain imaging in gastroenterology: to new beginnings

With more than 100 studies published over the past two decades, functional brain imaging research in gastroenterology has become an established field; one that has enabled improved insight into the supraspinal responses evoked by gastrointestinal stimulation both in health and disease. However, there remains considerable inter-study variation in the published results, largely owing to methodological differences in stimulation and recording techniques, heterogeneous patient selection, lack of control for psychological factors and so on. These issues with reproducibility, although not unique to studies of the gastrointestinal tract, can lead to unjustified inferences. To obtain consistent and more clinically relevant results, there is a need to optimize and standardize brain imaging studies across different centres. In addition, the use of complementary and more novel brain imaging modalities and analyses, which are now being used in other fields of research, might help unravel the factors at play in functional gastrointestinal disorders. This Review highlights the areas in which functional brain imaging has been useful and what it has revealed, the areas that are in need of improvement, and finally suggestions for future directions.