The Effectiveness of Hypnoanalgesia Using Conventional and Placebo Hypnosis Induction

The effectiveness of hypnosis-based pain management is well-established. However, mechanisms of action and specific effective components are not well understood. The sociocognitive theory of hypnosis proposes that the effectiveness of hypnosis for pain management is determined by the nonspecific features of response expectancy and context. We tested this claim by contrasting the effectiveness of 2 hypnoanalgesia procedures in a within subjects design using the cold pressor task. The 2 procedures were identical, including analgesic suggestions, except for the hypnosis induction used. One condition involved a well-established hypnosis induction, including suggestions for focused attention, relaxation, and deepening. The other condition included a sham induction procedure using only white noise. In our confirmatory analysis (N = 46), we found that pain tolerance increased compared to baseline equivalently in the conventional and sham induction conditions (mean increase 13.7 and 12.4 seconds respectively, average within subject difference -1.27 seconds, 90% confidence interval [CI] = -8.46, 5.90). This finding supports the claim of the sociocognitive theory considering that response expectancy for pain reduction was also equivalent between the conditions (average difference 2.30, 90% CI = -2.23, 6.84). However, self-reported hypnosis depth was greater in the conventional induction condition (average difference -.78, 90% CI: -1.36, -.07), which contradicts sociocognitive predictions. Our findings indicate that conventional procedural elements of hypnosis inductions, such as suggestions for focused attention, relaxation, and deepening, may not be necessary to achieve acute pain reduction in an experimental setting when the hypnosis intervention includes analgesic suggestions. PERSPECTIVE: This study assessed the necessary effective components of hypnosis-based analgesia interventions. Our findings suggest that procedural features such as suggestions for focused attention, relaxation, and deepening may not be necessary for hypnoanalgesia as long as pain relief suggestions are present, and the hypnosis context and response expectancy are established. TRIAL REGISTRATION: This trial was registered on Open Science Framework with the registry number e96xk, available at https://osf.io/e96xk.

Blood flow restriction augments exercise-induced pressure pain thresholds over repetition and effort matched conditions

We sought to determine the effects of blood flow restriction (BFR) on exercise-induced hypoalgesia, specifically using low-load (LL) resistance exercise (30% 1RM) protocols that accounted for each individual's local muscular endurance capabilities. Forty-four participants completed four conditions: (1) 70% of maximal BFR repetitions with blood flow restriction (LL+BFR exercise); (2) 70% maximal BFR repetitions without LL+BFR (LL exercise); (3) 70% maximal free flow repetitions (LL+EFFORT exercise); (4) time-matched, non-exercise control (CON). Pressure pain threshold (PPT) was measured before and after exercise. Ischaemic pain threshold and tolerance was assessed only at post. The change in upper body PPT was greater for LL+BFR exercise compared to LL exercise [difference of 0.15 (0.35) kg/cm2], LL+EFFORT exercise [difference of 0.23 (0.45) kg/cm2], and the CON condition. The change in lower body PPT was greater for LL+BFR exercise compared to LL exercise [difference of 0.40 (0.55) kg/cm2], LL+EFFORT exercise [difference of 0.36 (0.62) kg/cm2], and the CON condition. Ischaemic pain thresholds and tolerances did not change. Submaximal exercise with BFR resulted in systemic increases in PPT but had no influence on ischaemic pain sensitivity. This effect is likely unique to BFR as we did not see changes in the effort matched free flow condition.

Changes in pain perception during pregnancy after one-time maximal physical exertion and an 8-week high-intensity interval training

Background: Pain, a subjective sensation, poses a great challenge to the human body as a stressor. There is empirical evidence that moderate to intense physical activity increases pain tolerance and this may be critical during pregnancy for optimal pregnancy, fetal development, and delivery. To the best of our knowledge, it is the first study examining the changes in pain perception in pregnant women after a maximal progressive exercise test and after 8 weeks of high-intensity interval training (HIIT). Methods: Thirty-five women with uncomplicated singleton pregnancies between 13 and 28 weeks of gestation participated in the study. The HIIT intervention was developed in accordance with the recommendations and available data on HIIT during pregnancy. The maximal progressive cardiopulmonary exercise test was performed on a cycle ergometer with an electronically controlled load. Pressure pain threshold and pressure pain tolerance were measured with an algometer. Results: We found significant effects of the maximal exercise test and high-intensity interval training, such that the pregnant women had higher pain tolerance after the maximal exercise test than before and after the high-intensity interval training than the baseline. Conclusion: Our results suggest that post-exercise analgesia may be important in pregnant women and that high-intensity interval training appears to be beneficial for pregnant women to improve their pain tolerance while being obstetrically safe. Increased pain tolerance before labor could lead to better management of pain during labor and in the postpartum and lactation periods. Increasing pregnant women's awareness of this issue can improve their wellbeing and provide more comfort during labor.

Using a high-frequency carrier does not improve comfort of transcutaneous spinal cord stimulation

Objective.Spinal cord neuromodulation has gained much attention for demonstrating improved motor recovery in people with spinal cord injury, motivating the development of clinically applicable technologies. Among them, transcutaneous spinal cord stimulation (tSCS) is attractive because of its non-invasive profile. Many tSCS studies employ a high-frequency (10 kHz) carrier, which has been reported to reduce stimulation discomfort. However, these claims have come under scrutiny in recent years. The purpose of this study was to determine whether using a high-frequency carrier for tSCS is more comfortable at therapeutic amplitudes, which evoke posterior root-muscle (PRM) reflexes.Approach.In 16 neurologically intact participants, tSCS was delivered using a 1 ms long monophasic pulse with and without a high-frequency carrier. Stimulation amplitude and pulse duration were varied and PRM reflexes were recorded from the soleus, gastrocnemius, and tibialis anterior muscles. Participants rated their discomfort during stimulation from 0 to 10 at PRM reflex threshold.Main Results.At PRM reflex threshold, the addition of a high-frequency carrier (0.87 ± 0.2) was equally comfortable as conventional stimulation (1.03 ± 0.18) but required approximately double the charge to evoke the PRM reflex (conventional: 32.4 ± 9.2µC; high-frequency carrier: 62.5 ± 11.1µC). Strength-duration curves for tSCS with a high-frequency carrier had a rheobase that was 4.8× greater and a chronaxie that was 5.7× narrower than the conventional monophasic pulse, indicating that the addition of a high-frequency carrier makes stimulation less efficient in recruiting neural activity in spinal roots.Significance.Using a high-frequency carrier for tSCS is equally as comfortable and less efficient as conventional stimulation at amplitudes required to stimulate spinal dorsal roots.

Effectiveness of spontaneous pain coping strategies for acute pain management: A laboratory study

The aim of the present study has been to analyze the relationship between the use of not previously trained, diverse acute pain coping strategies and levels of pain intensity and pain tolerance in a group of healthy participants. Previous research has analyzed the usefulness of the training of these strategies after several training sessions, but adequate patient training requires a great deal of time. Two hundred and forty healthy people participated in the study. Pain coping strategies was evaluated with a version of CSQ-S. Subsequently, the participants completed a cold pressor test and tolerance test. After that, subjects filled in the adaptation of the CSQ-S about the strategies which they had employed throughout the test. Correlation analyses showed a positive relationship between pain intensity and catastrophizing, distractor behaviors, hoping and ignoring the pain. Pain tolerance correlated with self-instructions, ignoring the pain, reinterpreting the pain, catastrophizing and faith and praying. Regression analyses showed that catastrophizing was found to be the strategy that most predicts the variance of pain intensity, and catastrophizing (negative) and ignoring the pain (positive) and praying (negative) were the most predictive ones for pain tolerance. This is the first laboratory study that identifies the more useful pain coping strategies which can be used by patients without previous training in an acute pain context. The results of this study could be useful in the development of protocols for nurses and other health professionals, especially for situations where potentially painful techniques are to be applied to patients.

Pain processing and antisocial behavior: A multimodal investigation of the roles of boldness and meanness

Antisocial behavior has been linked to an increased tolerance of painful stimuli; however, there is evidence that pain behavior is multidetermined. The current study used pain measures from 3 different modalities (pain tolerance, pain ratings, electrocortical reactivity) and assessed triarchic traits of boldness and meanness to clarify the dispositional basis of associations between pain processing and antisocial behavior. High boldness was significantly associated with blunted early neural response to painful and nonpainful stimuli as well as increased pain tolerance. High meanness was associated with blunted elaborative processing of painful images, lower ratings of perceived pain for self and others, and increased pain tolerance. Meanness also accounted for variance shared between pain processing and antisocial behavior. Findings demonstrate that boldness and meanness contribute to pain processing in different ways and suggest that meanness may uniquely account for the association between blunted pain processing and antisocial behavior. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

"No pain, no gain": The impact of autonomous sensory meridian response on pain perception

Autonomous sensory meridian response (ASMR) is a phenomenon characterised by a static-like tingling sensation spreading from the scalp and neck to the periphery in response to a variety of audio, visual, and tactile triggers resulting in a highly relaxed state and boosted positive affect. The limited literature on this phenomenon points to a potential of ASMR to alleviate pain. Emerging evidence also suggests that ASMR may be linked to increased sensory sensitivity more broadly. This study aimed to objectively address these claims by administering an algometer (measure of pain tolerance), and a visual analog scale (VAS) (measure of subjective pain sensitivity) to ASMR experiencers and controls at baseline, following an ASMR video, and a control video. Findings indicate that ASMR experiencers have a higher pain sensitivity than controls; however, there was no difference between the two groups in terms of pain tolerance. In addition, any potential analgesic properties associated with experiencing ASMR may reflect protective properties of ASMR buffering against the increased pain sensitivity among ASMR experiencers relative to controls.

Analgesic Effect of Alcohol Mediates the Association between Alcohol Intoxication and Deliberate Self-Harm

We examined whether the analgesic effect of alcohol mediates the association between alcohol and deliberate self-harm (DSH) using data from a larger study on alcohol effects. Men (n = 106) and women (n = 104) low-risk alcohol drinkers (ages M = 26.00, SD = 6.98) recruited from the community who had no suicide attempt or episode of deliberate self-harm within the past year were randomly assigned to either a placebo drink condition or a drink calibrated to reach approximately .050%, .075%, or .100% blood alcohol concentration. Notable within-condition BAC variability, as well as overlap between conditions, suggested that BAC would be a more accurate indicator of intoxication compared to condition assignment. Pain tolerance was assessed by increasingly intense 1-s shocks delivered via fingertip electrodes. Self-reported pain associated with the pain tolerance index was also examined. A laboratory task of DSH, the Self-Aggression Paradigm, was then completed, with DSH operationalized as the number of self-administered shocks the participant was led to believe were twice the intensity of his or her pain tolerance and could cause "minor tissue damage that would quickly heal." A negative binomial parallel mediational model for count data revealed that pain tolerance, but not self-report pain, mediated the effect of alcohol on DSH. As such, the current study provides preliminary experimental evidence that the analgesic effect of alcohol is partially responsible for link between alcohol intoxication and deliberate self-harm.

To tolerate weather and to tolerate pain: two sides of the same coin? The Tromsø Study 7

ABSTRACT

It is a common belief that weather affects pain. Therefore, we hypothesized that weather can affect pain tolerance. This study used data from over 18,000 subjects aged 40 years or older from the general population, who participated in the Tromsø Study 7. They underwent a one-time assessment of cuff algometry pressure pain tolerance (PPT) and cold pain tolerance (CPT), tested with a cold pressor test. The results showed a clear seasonal variation in CPT. The rate of withdrawal in the cold pressor test was up to 75% higher in months in the warmer parts of the year compared with January 2016. There was no seasonal variation in PPT. The study not only found a nonrandom short-term variation in PPT but also indications of such a variation in CPT. The intrinsic timescale of this short-term variation in PPT was 5.1 days (95% % confidence interval 4.0-7.2), which is similar to the observed timescales of meteorological variables. Pressure pain tolerance and CPT correlated with meteorological variables, and these correlations changed over time. Finally, temperature and barometric pressure predicted future values of PPT. These findings suggest that weather has a causal and dynamic effect on pain tolerance, which supports the common belief that weather affects pain.

The induction of social pessimism reduces pain responsiveness

OBJECTIVES

Past work has found that optimism reduces a person's responsiveness to pain, but the effects of pessimism are not clear. Therefore, we gave pessimistic forecasts of participants' future social life and measured changes in their pain responsiveness. In particular, some participants were told that they would end up alone in life.

METHODS

Seventy-five subjects were investigated in three conditions (negative forecast, positive forecast, no forecast) for changes in pain threshold and pain tolerance threshold. Pressure pain induction was accomplished by either human- or machine-driven algometers. A randomly assigned bogus forecast promising either a lonely or a socially satisfying future was ostensibly based on a personality questionnaire and an emotional dot-probe task. As potential covariates, questionnaires assessing dispositional optimism (LOT-R), pain catastrophizing (PCS), and self-esteem (SISE) were given.

RESULTS

Pain thresholds suggested a change toward unresponsiveness only in the negative forecast condition, with only small differences between the modes of pain induction (i.e., human or machine). The results for pain tolerance thresholds were less clear also because of limiting stimulation intensity for safety reasons. The covariates were not associated with these changes.

CONCLUSIONS

Thus, people expecting a lonely future became moderately less responsive to pain. This numbing effect was not modulated by personality measures, neither in a protective fashion via dispositional optimism and self-esteem nor in a risk-enhancing fashion via trait pain catastrophizing. Alternative mechanisms of action should be explored in future studies.

Both Gender and Agonistic Experience Affect Perceived Pain during the Cold Pressor Test

Background. Differences in pain perception in athletes have recently been highlighted in the literature. Objectives. To compare gender ratings of perceived pain in athletes with low and high agonistic experiences (N = 200) using the Cold Pressor Test (CPT). Methods. A three-way repeated measures ANOVA to assess both the effects of the athletes’ gender and lower vs. higher agonistic experiences in the intensity of perceived pain at the beginning of the cold box hand immersion (L₀) and after a 90 s interval (L₁). Results. There was a statistically significant interaction effect between the level of the agonistic experience and gender in the two moments: p < 0.001; η_p² = 0.266; F(1,49) = 9.771. Simple main effects analysis showed a significative difference for females at L₀: F(1,99) = 93.567, p < 0.025, partial η² = 0.302) and for males at L₁: F(1,99) = 173.420, p < 0.025, partial η² = 0.666. At the initial moment of CPT, the female athletes showed significantly higher perceived intensity than males, regardless of their experience level. After a 90 s interval, a significantly lower pain perception effect associated with the increased competitive experience of male athletes was observed. Female athletes did not appear to benefit from the experience effect on their pain tolerance. Conclusions. The study confirmed a significant difference in pain perception associated with the athletes’ gender and agonistic experience. Separate explanations related to the pattern of pain inhibition and the acquired reduction in pain sensitivity are reported.

Alexithymia increases effects of ego-depletion

Alexithymia is associated with deficiencies to identify, describe and express emotions, paucity of fantasies and an externally oriented cognitive style. The current studies provide evidence that alexithymia is also related to self-regulation processes and exacerbates effects of ego-depletion, a state where self-regulation resources are reduced due to previous acts of self-regulation. In Study 1, ego-depletion effects of a handgrip task on pain tolerance were increased by alexithymia. In Study 2, an emotion suppression task showed stronger effects of ego-depletion on a Stroop task in participants high rather than low in alexithymia, but only after suppression of emotions induced by negative and not positive pictures. The results imply that alexithymia increases susceptibility to ego-depletion effects, that consumption of self-regulatory resources has stronger consequences for people high in alexithymia and that they should experience special support in ways to replenish self-regulation resources.

Virtual Reality as a Pain Distraction Modality for Experimentally Induced Pain in a Chronic Pain Population: An Exploratory Study

Virtual reality (VR) has shown promising results as an adjunct therapy for pain management. Recent literature exploring the use of VR for pain management among a chronic pain (CP) population has produced encouraging results, although little has been done to explore what about a VR intervention is the provider of the analgesic response. Furthermore, as has been suggested in the literature previously, little has been said of the association between pain tolerance and presence. This study primarily aimed to investigate pain tolerance differentiation between VR-head-mounted display (HMD) active and control interventions. Secondarily, this study looked to report on whether presence correlates to pain tolerance, among a CP population. A repeated-measures study design was used. Twelve participants received two 5-minute interventions while being subjected to experimentally induced pain. The interventions were as follows: (a) "active intervention," an immersive and interactive experience (b) "control intervention," and a nonimmersive controlled experience with no interaction. Tolerance to pain was assessed via the total time the participant continued the intervention. Presence was assessed via the Witmer and Singer's presence questionnaire. Participants also completed the Simulator Sickness Questionnaire, the Presence Questionnaire, and the Brief Pain Inventory. Pain tolerance was significantly higher in the active intervention compared with the control intervention (p = 0.005). There was a positive correlation between pain tolerance and presence during the active VR intervention. The media as opposed to the medium was determined to be responsible for greater tolerance to pain, as well as greater sense of presence, which was positively correlated to an increase in pain tolerance.

Are all pain tolerance tasks the same? Convergent validity of four behavioral pain tolerance tasks, self-reported capability for suicide, and lifetime self-injurious behaviors

OBJECTIVES

Discrepancies persist regarding the extent to which different pain measures provide similar information and relate to capability for suicide and self-injurious behaviors. This study examined pain threshold, tolerance, and persistence across four modalities (cold, heat, pressure, shock) and assessed associations with self-reported capability for suicide, non-suicidal self-injury (NSSI), and suicide attempts.

METHODS

A sample of 211 students who reported lifetime suicidal ideation completed four behavioral pain tasks and self-reported on capability for suicide, NSSI, and self-injurious behaviors.

RESULTS

All pain thresholds, tolerances, and persistences were positively correlated across the four tasks. Pain facets were related to self-reported capability for suicide with small effect sizes but generally did not differ across suicide attempt or NSSI histories.

CONCLUSIONS

Pain thresholds, tolerances, and persistences demonstrated convergent validity across the four modalities, suggesting that these tasks provide similar information. Although the relation between pain and self-injurious behaviors remains unclear, these tasks can generally be used interchangeably.

Clarifying the Relationship of Dissociative Experiences to Suicide Ideation and Attempts: A Multimethod Examination in Two Samples

Fears of pain, injury, and death may represent key barriers to acting on suicidal thoughts. Dissociation, which involves a disconnection from one's body, may reduce fears and sensations of pain associated with harming the body, in turn facilitating suicide attempts. This study examined whether dissociation differentiated individuals with a history of suicide attempts from those with a history of suicide ideation, and investigated whether other relevant constructs explain this relationship. Sample 1 included 754 undergraduates (M_age = 21, 79% female) who completed a battery of self-report measures. Sample 2 included 247 undergraduates (M_age = 19, 74% female) who completed a self-report measure of dissociation, a clinical interview regarding suicide history, and four counterbalanced behavioral pain tolerance tasks. In both samples, dissociation was elevated in lifetime attempters compared to ideators (d = 0.28; d = 0.46; ps = 0.01) and slightly elevated in lifetime ideators compared to nonsuicidal individuals (d = 0.19, p = .02; d = 0.24, p = .47), though this effect was non-significant in the latter sample. In Sample 1, dissociation no longer differentiated attempters from ideators after controlling for clinical covariates. In Sample 2, dissociation was unrelated to behavioral pain tolerance tasks, and these tasks did not account for the association between dissociation and attempts. Overall, dissociation differentiated individuals with a history of suicide attempts from those with ideation alone in both samples. Pain tolerance did not explain this association; instead, it is possible that the relationship of dissociation to suicide attempts is due to "third variables" associated with both phenomena, such as symptoms of borderline personality disorder or posttraumatic stress disorder.

Interoception, Pain Tolerance, and Self-Injurious Behaviors: A Multidimensional Assessment

Impairments in interoception have been linked to self-injurious behaviors, and capability for suicide may account for this relationship. However, past studies have relied primarily on self-report and unidimensional measures. The present study aimed to replicate and extend previous findings by examining the relationship between interoceptive dysfunction, pain tolerance, and self-injurious behaviors using a multidimensional and multi-method approach. A sample of 245 undergraduate students (M_age = 19.27 years, SD = 2.81; 73.7% female, 72.% White/European American), who reported lifetime suicidal ideation on a screening survey completed a battery of self-report measures, four counterbalanced pain tolerance tasks, and a clinical interview assessing their self-injurious behaviors. A tendency to stay attuned to bodily sensations was significantly related to decreased pain tolerance. Only trust in one's body was significantly related to decreased presence of lifetime suicide attempts. No other facets of interoception or pain tolerance were significantly associated with self-injurious behaviors. Overall, these findings contrast with previous findings that capability for suicide may account for relations between interoceptive dysfunction and self-injurious behaviors. Nonetheless, the results of this study provide important information on the factor structure of interoceptive dysfunction and pain tolerance, and highlight the importance of careful selection of measures and operationalization of key constructs, particularly interoceptive dysfunction and pain tolerance.

Influence of Cognitive Orientation and Attentional Focus on Pain Perception

Background. Recently, a growing interest has emerged in the role of attention and hypervigilance in the experience of pain. Shifting attention away from pain seems likely to reduce the perception of pain itself. Objectives. The present study has been designed to test the following overall hypotheses: (1) disposition to catastrophize, self-efficacy perceived in pain resistance (task self-efficacy), previous experiences concerning the tolerance of physical pain, and degree of impulsiveness are significant predictors of the decision to abandon a painful test such as the cold pressor test (CPT); (2) the manipulation of the attentive focus (internal or external) can influence the level of perceived pain. Methods. Effects of the manipulation of attentional focus (internal and external) on pain perception and response of trial abandonment were evaluated in a sample of university students (n = 246) subjected to the cold pressor test. Results. A significant effect (p < 0.05) was found through a test–retest comparison on the final level of perceived pain among subjects who had received instruction to externalize the focus of their attention (mixed factorial analysis of variance), but no significance was observed with respect to the decision to abandon the experiment. A general explanatory model of the abandonment behavior demonstrating overall good fit measurements was tested too. Conclusion. The abandonment of tests has been shown to be predicted mainly by catastrophic attitude. Attentive impulsiveness showed a further positive effect on catastrophic attitude. Perceived self-efficacy in the tolerance of pain limited learned helplessness, which in turn positively influenced catastrophizing.

Blunted Pain Modulation Response to Induced Stress in Women with Fibromyalgia with and without Posttraumatic Stress Disorder Comorbidity: New Evidence of Hypo-Reactivity to Stress in Fibromyalgia?

There is evidence regarding the presence of alterations in both the stress response and the endogenous pain modulation systems of people with fibromyalgia (FM). However, research on pain modulation under induced stress on FM patients is scarce and contradictory. The present study analyzes stress-induced changes in pain and intolerance thresholds among FM patients, examining the possible existence of differences linked to PTSD comorbidity and gaining insights into the role of cardiovascular reactivity. Eighteen women diagnosed with FM and comorbid PTSD (FM + PTSD), 18 women diagnosed with FM and no PTSD (FM-PTSD), and 38 healthy women (HC) were exposed to the Social Stress Test task. Pressure pain thresholds and intolerance thresholds were measured before and during stress induction, and after a recovery period, while systolic blood pressure and heart rate were simultaneously recorded. Overall, while pain thresholds decreased during stress and recovery for HC, no significant changes were observed for women with FM. The intolerance threshold decreased for HC during stress, but was maintained at basal level during recovery. FM-PTSD women exhibited a delayed response, with a drop at recovery. For FM + PTSD, tolerance levels remained unchanged. In addition, cardiovascular reactivity did not seem to explain these results. This performance of the pain modulation system seems to follow the same pattern of hypoactive responsiveness under stressors that has previously been observed in FM patients on the autonomic and neuroendocrine axes. Such a hypoactive pattern may involve a non-adaptive response that may contribute to the development and maintenance of chronic pain.

Investigation of the Less Known Effects of Manual Lymphatic Drainage: A Narrative Review

Introduction: Manual lymphatic drainage (MLD), one of the components of complex decongestive physiotherapy, which is accepted as the gold standard in the treatment of lymphedema, is used for therapeutic purposes in many diseases. The most well-known feature of MLD is that it helps to reduce edema. In addition to reducing edema, MLD has many effects, such as increasing venous flow, reducing fatigue, and raising the pain threshold. To the best of our knowledge, there is no study examining the effects of MLD other than its effects on edema in detail. The aim of this study is to compile effects of MLD and to provide a better understanding of the effects of MLD. Methods: A literature search was conducted in Medline, Embase, and the Cochrane Library in July 2019, to identify different effects of MLD. The articles were chosen by, first, reading the abstract and subsequently data were analyzed by reading the entire text through full-text resources. To undertake the study, we have collected information published about different effects of MLD over the last 30 years (1989-2019). According to our results, 20 studies met inclusion criteria. Conclusions: This study suggests that MLD can be used in symptomatic treatment of various diseases (multiple sclerosis, Parkinson's disease) considering the effects of MLD on the systems.

Attenuating Pain With the Past: Nostalgia Reduces Physical Pain

Previous work has found that nostalgia, a sentimental longing for the past, is associated with psychological, emotional, and social benefits. Recent research has demonstrated that nostalgic reflection also can improve individuals’ physical health (i.e., exercise) and reduce temperature-related pain. Building on this, two experiments examined how nostalgia can reduce people’s pain perceptions (i.e., reduced severity and increased tolerance). Specifically, Study 1 showed that inducing nostalgia through a writing task decreased perceived pain severity (i.e., intensity) among self-reported chronic pain sufferers. Study 2, in turn, demonstrated that Japanese individuals experienced increased pain tolerance (i.e., the maximum level of pain a person can tolerate) for a pressure algometer task following thoughts of nostalgia (vs. a control prime). This work provides evidence that nostalgic reflection may serve as a psychological resource to reduce the perceived severity of physical pain.

Kratom and Pain Tolerance: A Randomized, Placebo-Controlled, Double-Blind Study

Background: Kratom has a long history of traditional medicine use in Southeast Asia. Consumption of kratom products has also been reported in the US and other regions of the world. Pain relief is among many self-reported kratom effects but have not been evaluated in controlled human subject research. Methods: Kratom effects on pain tolerance were assessed in a randomized, placebo-controlled, double-blind study. During a 1-day inpatient stay, participants received a randomized sequence of kratom and placebo decoctions matched for taste and appearance. Pain tolerance was measured objectively in a cold pressor task (CPT) as time (seconds) between the pain onset and the hand withdrawal from the ice bath. Health status, vital signs, objective, and subjective indicators of withdrawal symptoms, self-reported data on lifetime kratom use patterns, and assessments of blinding procedures were also evaluated. Results: Twenty-six males with the mean (SD) age 24.3 (3.4) years were enrolled. They reported the mean (SD) 6.1 (3.2) years of daily kratom consumption. Pain tolerance increased significantly 1 hour after kratom ingestion from the mean (SD) 11.2 (6.7) seconds immediately before to 24.9 (39.4) seconds 1 hour after kratom consumption (F(2,53.7)=4.33, p=0.02). Pain tolerance was unchanged after consuming placebo drinks: 15.0 (19.0) seconds immediately before and 12.0 (8.1) seconds 1 hour after consumption of placebo (F(2,52.8)=0.93, p=0.40). No discomfort or signs of withdrawal were reported or observed during 10-20 hours of kratom discontinuation. Conclusions: Kratom decoction demonstrated a substantial and statistically significant increase in pain tolerance. Further rigorous research on kratom pain-relieving properties and a safety profile is needed.

Swearing as a Response to Pain: Assessing Hypoalgesic Effects of Novel "Swear" Words

Previous research showing that swearing alleviates pain is extended by addressing emotion arousal and distraction as possible mechanisms. We assessed the effects of a conventional swear word (“fuck”) and two new “swear” words identified as both emotion-arousing and distracting: “fouch” and “twizpipe.” A mixed sex group of participants (N = 92) completed a repeated measures experimental design augmented by mediation analysis. The independent variable was repeating one of four different words: “fuck” vs. “fouch” vs. “twizpipe” vs. a neutral word. The dependent variables were emotion rating, humor rating, distraction rating, cold pressor pain threshold, cold pressor pain tolerance, pain perception score, and change from resting heart rate. Mediation analyses were conducted for emotion, humor, and distraction ratings. For conventional swearing (“fuck”), confirmatory analyses found a 32% increase in pain threshold and a 33% increase in pain tolerance, accompanied by increased ratings for emotion, humor, and distraction, relative to the neutral word condition. The new “swear” words, “fouch” and “twizpipe,” were rated as more emotional and humorous than the neutral word but did not affect pain threshold or tolerance. Changes in heart rate and pain perception were absent. Our data replicate previous findings that repeating a swear word at a steady pace and volume benefits pain tolerance, extending this finding to pain threshold. Mediation analyses did not identify a pathway via which such effects manifest. Distraction appears to be of little importance but emotion arousal is worthy of future study.

The relationship between maximum tolerance and motor activation during transcutaneous spinal stimulation is unaffected by the carrier frequency or vibration

Transcutaneous spinal stimulation (TSS) is a useful tool to modulate spinal sensorimotor circuits and has emerged as a potential treatment for motor disorders in neurologically impaired populations. One major limitation of TSS is the discomfort associated with high levels of stimulation during the experimental procedure. The objective of this study was to examine if the discomfort caused by TSS can be alleviated using different stimulation paradigms in a neurologically intact population. Tolerance to TSS delivered using conventional biphasic balanced rectangular pulses was compared to two alternative stimulation paradigms: a 5 kHz carrier frequency and biphasic balanced rectangular pulses combined with vibrotactile stimulation. In ten healthy participants, tolerance to TSS was examined using both single-pulse (0.2 Hz) and continuous (30 Hz) stimulation protocols. In both the single-pulse and continuous stimulation protocols, participants tolerated significantly higher levels of stimulation with the carrier frequency paradigm compared to the other stimulation paradigms. However, when the maximum tolerable stimulation intensity of each stimulation paradigm was normalized to the intensity required to evoke a lower limb muscle response, there were no statistical differences between the stimulation paradigms. Our results suggest that, when considering the intensity of stimulation required to obtain spinally evoked motor potentials, neither alternative stimulation paradigm is more effective at reducing discomfort than the conventional, unmodulated pulse configuration.

Interoceptive deficits, non-suicidal self-injury, and suicide risk: a multi-sample study of indirect effects

BACKGROUND

Interoceptive deficits (ID) have been associated with non-suicidal self-injury (NSSI) and suicidal behavior in multiple studies. Many of these studies are limited in scope, and have not fully examined possible mechanisms explaining how ID affect suicidal behavior.

METHODS

This study assesses how self-reported ID relate to suicide ideation and attempts in six distinct and geographically diverse samples of adults (n = 2706) and one sample of adolescents (n = 436). Participants responded to a variety of self-report questionnaires and interviews.

RESULTS

Contrary to our hypothesis, self-reported ID were only associated with suicidal ideation in two samples, one of which was the adolescent sample. Largely consistent with our predictions, self-reported ID exhibited an indirect effect on suicide attempts through versatility of NSSI in four of the five adult samples tested. Finally, the indirect effects of self-reported ID on suicide attempts through NSSI versatility did not act indirectly through behaviorally assessed pain tolerance.

CONCLUSIONS

We found that, in adults, self-reported ID are not associated with suicidal ideation, but are connected with a history of suicide attempts, through an indirect effect via NSSI. Our findings also indicate that the mechanism of action leading from self-reported ID to suicidal behavior may differ between adolescents and adults, and relate to suicidal behavior independent of pain tolerance. Clinical implications and future directions are discussed.

The mechanisms of pain tolerance and pain-related anxiety in acute pain

This study emphasizes the role of pain catastrophizing and state anxiety on pain tolerance and pain-related anxiety. Response expectancies for pain tolerance and pain intensity were tested as potential mediators. A cold-pressor task was used on a healthy sample. Measures were taken before and after cold-pressor procedure, while aversive versus neutral information regarding the cold-pressor task was given prior to the pain induction. An exploratory path model was conducted. Similar paths for pain tolerance and for pain-related anxiety were shown in aversive condition. Also, psychological measures may explain pain experience in aversive context.

Racial differences in experimental pain sensitivity and conditioned pain modulation: a study of Chinese and Indians

Background: Substantial literature has demonstrated racial differences in pain perception and endogenous pain modulation is proposed to be a mechanism for the racial differences. Although Indians in Singapore reported higher pain severity than Chinese, the only study on racial difference in experimental pain response in Singapore did not find any difference between the two racial groups. Purpose: The aim of this study was to investigate pain sensitivity and conditioned pain modulation in Chinese and Indians in Singapore. Patients and methods: Sixty age-and sex-matched (30 Chinese 50% female, 30 Indian, 50% female) healthy adults participated in this study. Pressure pain threshold, thermal pain threshold and cold pain tolerance were measured. Conditioned pain modulation, general self-efficacy and depression were also tested, in an attempt to assess endogenous pain inhibition and psychological presentation between the two groups. Results: No difference in pain thresholds was found between the two groups. Indians demonstrated less cold pain tolerance and less efficacious conditioned pain modulation than Chinese. Conditioned pain modulation was a mediator between race and cold pain tolerance. Conclusion: These findings of racial disparities in pain tolerance and endogenous pain inhibition could possibly contribute to the higher pain severity in Indians.

The peer effect on pain tolerance

Background and aims Twin studies have found that approximately half of the variance in pain tolerance can be explained by genetic factors, while shared family environment has a negligible effect. Hence, a large proportion of the variance in pain tolerance is explained by the (non-shared) unique environment. The social environment beyond the family is a potential candidate for explaining some of the variance in pain tolerance. Numerous individual traits have previously shown to be associated with friendship ties. In this study, we investigate whether pain tolerance is associated with friendship ties. Methods We study the friendship effect on pain tolerance by considering data from the Tromsø Study: Fit Futures I, which contains pain tolerance measurements and social network information for adolescents attending first year of upper secondary school in the Tromsø area in Northern Norway. Pain tolerance was measured with the cold-pressor test (primary outcome), contact heat and pressure algometry. We analyse the data by using statistical methods from social network analysis. Specifically, we compute pairwise correlations in pain tolerance among friends. We also fit network autocorrelation models to the data, where the pain tolerance of an individual is explained by (among other factors) the average pain tolerance of the individual's friends. Results We find a significant and positive relationship between the pain tolerance of an individual and the pain tolerance of their friends. The estimated effect is that for every 1 s increase in friends' average cold-pressor tolerance time, the expected cold-pressor pain tolerance of the individual increases by 0.21 s (p-value: 0.0049, sample size n=997). This estimated effect is controlled for sex. The friendship effect remains significant when controlling for potential confounders such as lifestyle factors and test sequence among the students. Further investigating the role of sex on this friendship effect, we only find a significant peer effect of male friends on males, while there is no significant effect of friends' average pain tolerance on females in stratified analyses. Similar, but somewhat lower estimates were obtained for the other pain modalities. Conclusions We find a positive and significant peer effect in pain tolerance. Hence, there is a significant tendency for students to be friends with others with similar pain tolerance. Sex-stratified analyses show that the only significant effect is the effect of male friends on males. Implications Two different processes can explain the friendship effect in pain tolerance, selection and social transmission. Individuals might select friends directly due to similarity in pain tolerance, or indirectly through similarity in other confounding variables that affect pain tolerance. Alternatively, there is an influence effect among friends either directly in pain tolerance, or indirectly through other variables that affect pain tolerance. If there is indeed a social influence effect in pain tolerance, then the social environment can account for some of the unique environmental variance in pain tolerance. If so, it is possible to therapeutically affect pain tolerance through alteration of the social environment.

Psychological Factors Associated With Ultramarathon Runners' Supranormal Pain Tolerance: A Pilot Study

Athletes seem to have higher pain tolerance than the normally active population. It is unknown whether psychological factors contribute to their supranormal pain tolerance. The aim of this pilot study was to examine pain-related psychological processes in ultramarathon runners ('ultrarunners') and to explore whether psychological factors mediate the elevated pain tolerance displayed by ultrarunners. Forty participants took part in the study: 20 ultrarunners and 20 age- and gender-matched controls. Participants underwent the cold pressor test using water cooled to 0.1 to 0.5°C and completed the Pain Catastrophizing Scale, Pain Anxiety Symptoms Scale-20, Pain Vigilance and Awareness Questionnaire, and Pain Resilience Scale. Immersion time on the cold pressor test was significantly longer for the ultrarunners (P = .007) and they also had lower scores on all Pain Anxiety Symptoms Scale-20 subscales (P ≤ .030). The 2 groups did not differ significantly on the other questionnaires. Mediation analysis revealed that reduced pain-related escape and avoidance behaviors accounted for 40% of the difference in immersion time between the groups (P = .020). Our results suggest that ultrarunners have lower levels of pain-related anxiety than the general population and that their supranormal pain tolerance is partially mediated by reduced pain-related escape and avoidance behaviors. PERSPECTIVE: This study investigated whether psychological factors contribute to the supranormal pain tolerance displayed by ultrarunners. It found that ultrarunners have lower levels of pain-related anxiety than nonrunning controls and that reduced pain-related escape and avoidance behaviors partially mediate their elevated pain tolerance.

The Influence of a Personal Values Intervention on Cold Pressor-Induced Distress Tolerance

Research has demonstrated that values and acceptance interventions can increase distress tolerance, but the individual contribution of each remains unclear. The current study examined the isolated effect of a values intervention on immersion time in a cold pressor. Participants randomized to Values (n = 18) and Control (n = 14) conditions completed two cold pressor tasks, separated by a 30-min values or control intervention. Immersion time increased 51.06 s for participants in the Values condition and decreased by 10.79 s for those in the Control condition. Increases in self-reported pain and distress predicted decreases in immersion time for Control, but not Values, participants. The best-fitting model accounted for 39% of the variance in immersion time change. Results suggest that a brief isolated values exercise can be used to improve distress tolerance despite increased perceptions of pain and distress, such that values alone may be sufficient to facilitate openness to difficult experiences.

Glutamatergic Response to Heat Pain Stress in Schizophrenia

Regulation of stress response involves top-down mechanisms of the frontal-limbic glutamatergic system. As schizophrenia is associated with glutamatergic abnormalities, we hypothesized that schizophrenia patients may have abnormal glutamatergic reactivity within the dorsal anterior cingulate cortex (dACC), a key region involved in perception of and reaction to stress. To test this, we developed a somatic stress paradigm involving pseudorandom application of safe but painfully hot stimuli to the forearm of participants while they were undergoing serial proton magnetic resonance spectroscopy to measure changes in glutamate and glutamine levels in the dACC. This paradigm was tested in a sample of 21 healthy controls and 23 patients with schizophrenia. Across groups, glutamate levels significantly decreased following exposure to thermal pain, while ratio of glutamine to glutamate significantly increased. However, schizophrenia patients exhibited an initial increase in glutamate levels during challenge that was significantly different from controls, after controlling for heat pain tolerance. Furthermore, in patients, the acute glutamate response was positively correlated with childhood trauma (r = .41, P = .050) and inversely correlated with working memory (r = -.49, P = .023). These results provide preliminary evidence for abnormal glutamatergic response to stress in schizophrenia patients, which may point toward novel approaches to understanding how stress contributes to the illness.

Effect of Mindfulness Based Stress Reduction (MBSR) in Increasing Pain Tolerance and Improving the Mental Health of Injured Athletes

Literature indicates that injured athletes face both physical and psychological distress after they have been injured. In this study, a Mindfulness Based Stress Reduction (MBSR) was utilised as an intervention for use during the period of recovery with injured athletes and, to the best of our knowledge, this is the first study using MBSR as an intervention for this purpose. Objective: The aim of this research was to investigate the role of MBSR practise in reducing the perception of pain and decreasing anxiety/stress, as well as increasing pain tolerance and mindfulness. An additional aim was to increase positive mood and decrease negative mood in injured athletes. Methods: The participants comprised of twenty athletes (male = 14; female = 6; age range = 21-36 years) who had severe injuries, preventing their participation in sport for more than 3 months. Prior to their injury, the participants had trained regularly with their University teams and participated in official university championships. Both groups followed their normal physiotherapy treatment, but in addition, the intervention group practised mindfulness meditation for 8 weeks (one 90-min session/week). A Cold Pressor Test (CPT) was used to assess pain tolerance. In contrast, the perception of pain was measured using a Visual Analogue Scale. Other measurements used were the Mindful Attention Awareness Scale (MAAS), Depression Anxiety and Stress Scale (DASS), and Profile of Mood States (POMS). Results: Our results demonstrated an increase in pain tolerance for the intervention group and an increase in mindful awareness for injured athletes. Moreover, our findings observed a promising change in positive mood for both groups. Regarding the Stress/Anxiety scores, our findings showed a notable decrease across sessions; however, no significant changes were observed in other main and interaction effects in both groups. Conclusion: Injured athletes can benefit from using mindfulness as part of the sport rehabilitation process to increase their pain tolerance and awareness. Further research is required to assess whether increasing pain tolerance could help in the therapeutic process.

The Long-Term Footprint of Endometriosis: Population-Based Cohort Analysis Reveals Increased Pain Symptoms and Decreased Pain Tolerance at Age 46 Years

Previous studies have shown increased pain sensitivity in fertile-aged women with endometriosis in response to mechanical stimuli. As yet, population-based studies on the association of endometriosis with pain sensation and pain symptoms in late fertile age are lacking. The main objective of this population-based cohort study was to investigate whether a history of endometriosis is associated with altered pain sensation and musculoskeletal pain symptoms at age 46 years. Our data are derived from the Northern Finland Birth Cohort 1966, which contains postal questionnaire data (72% response rate) as well as clinical data assessing pressure-pain threshold and maximal pain tolerance. The study population consisted of 284 women with endometriosis and 3,390 controls. Our results showed that at age 46 women with a history of endometriosis had a 5.3% lower pressure-pain threshold and 5.1% lower maximal pain tolerance compared with controls. The most significant contributors besides endometriosis were anxiety, depression, and current smoking status. Women with endometriosis also reported an increased number of pain sites (0 pain sites, 9.6 vs 17.9%; 5-8 pain sites, 24.8 vs 19.1%, endometriosis vs controls respectively; P < .001), and their pain was more troublesome and intense. The results were adjusted for body mass index, smoking, depressive/anxiety symptoms, education, and use of hormonal contraceptives. These unique data revealed an altered pain sensation and a greater likelihood of reporting musculoskeletal pain at age 46 years among women with a history of endometriosis. The results imply that endometriosis has a long-term footprint on affected women, thus underlying the need for psychological support and medical treatment beyond fertile age.

PERSPECTIVE

This population-based cohort study showed decreased pain threshold and maximal pain tolerance in women with endometriosis in the late fertile age of 46 years. The pain was also found to be more bothersome and intense compared with controls.

Effects of Androgen Deprivation Therapy on Pain Perception, Quality of Life, and Depression in Men With Prostate Cancer

CONTEXT

Previous animal and human research suggests that testosterone has antinociceptive properties. Castration in male rodents increases pain perception which is reversed by testosterone replacement. Pain perception also improves in hypogonadal men with testosterone therapy. However, it remains unclear whether androgen deprivation therapy (ADT) in men with prostate cancer (PCa) is associated with an increase in pain perception.

OBJECTIVES

To evaluate the effects of ADT on pain perception, depression and quality of life (QOL) in men with PCa.

METHODS

Thirty-seven men with PCa about to undergo ADT with leuprolide acetate (ADT group) were followed prospectively for six months to evaluate changes in clinical and experimental pain. Forty men who had previously undergone prostatectomy for localized PCa and were in remission served as controls (non-ADT group). All participants were eugonadal at study entry. Primary outcomes were changes in clinical pain (assessed with Brief Pain Inventory questionnaire) and experimental pain (assessed with quantitative sensory testing). Secondary outcomes included evaluation of depression, anxiety levels, and quality of life.

RESULTS

Serum testosterone levels significantly decreased in the ADT group but remained unchanged in the non-ADT group. There were no significant changes in pain thresholds, ratings, or other responses to quantitative sensory tests over the 6-month course of the study. Clinical pain did not differ between the two groups, and no changes from baseline were observed in either group. Men undergoing ADT did experience worsening of depression (0.93; 95% CI = 0.04-1.82; P = 0.042) and QOL related to physical role limitation (-18.28; 95% CI = -30.18 to -6.37; P = 0.003).

CONCLUSION

ADT in men with PCa is associated with worsening of depression scores and QOL but is not associated with changes in clinical pain or pain sensitivity.

Individual differences in pain sensitivity predict the experience of unfairness

Pain has shaped our evolutionary history, and pain-free experiences are critical for our health. There are, however, enormous individual differences in pain sensitivity, and the psychological consequences of this heterogeneity are only poorly understood. Here, we investigated whether individual differences in pain sensitivity predicted the experience of unfairness. We found that the magnitude of pain sensitivity correlated with the extent to which participants experienced unfairness. This association was due to the shared human alarm system of unfairness and pain sensitivity. This finding may elucidate mechanisms for producing a new and positive cycle of a healthy experience between fairness and feeling pain-free.

A first-in-human, double-blind, placebo-controlled, randomized, dose escalation study of DWP05195, a novel TRPV1 antagonist, in healthy volunteers

Objectives

DWP05195 is a transient receptor potential vanilloid 1 (TRPV1) antagonist developed for managing pain. The purpose of this study was to evaluate the pharmacodynamics pharmacokinetics, safety, and tolerability of DWP05195 in healthy subjects. This was a first-in-human randomized, double-blinded, placebo-controlled, dose escalation study.

Subjects and methods

DWP05195 or placebo was administered as a single dose of 10–600 mg in the single-dose study and as 100–400 mg once daily for 8 days in the multiple-dose studies. Each study group consisted of 10 subjects (study drug-to-placebo ratio was 8:2). For pharmacodynamics assessment, the heat pain threshold (HPtr), heat pain tolerance (HPtol), perfusion intensity, and flare area ratio of cutaneous blood flow were measured. Safety and tolerability were evaluated throughout the study.

Results

The maximum plasma concentrations and area under the plasma concentration–time curve from zero to the last measurable time dose-dependently increased. HPtr and HPtol tended to increase more after DWP05195 administration than after placebo administration. HPtr and HPtol tended to dose-dependently increase after administration of DWP05195. Cutaneous blood flow was reduced as the dose of DWP05195 increased during the multiple-dose study. DWP05195 was well tolerated up to 600 and 400 mg single- and multiple-dose administrations, respectively.

Conclusion

The pharmacological activity of DWP05195, measured using HPtr and HPtol, increased as expected in a dose-dependent manner owing to increased systemic exposure, indicating that DWP05195 can be used as a TRPV1 antagonist for pain management.

Neurobiological Aspects of Mindfulness in Pain Autoregulation: Unexpected Results from a Randomized-Controlled Trial and Possible Implications for Meditation Research

Background: Research has demonstrated that short meditation training may yield higher pain tolerance in acute experimental pain. Our study aimed at examining underlying mechanisms of this alleged effect. In addition, placebo research has shown that higher pain tolerance is mediated via endogenous neuromodulators: experimental inhibition of opioid receptors by naloxone antagonized this effect. We performed a trial to discern possible placebo from meditation-specific effects on pain tolerance and attention. Objectives: It was proposed that (i) meditation training will increase pain tolerance; (ii) naloxone will inhibit this effect; (iii) increased pain tolerance will correlate with improved attention performance and mindfulness. Methods: Randomized-controlled, partly blinded trial with 31 healthy meditation-naïve adults. Pain tolerance was assessed by the tourniquet test, attention performance was measured by Attention Network Test (ANT), self-perceived mindfulness by Freiburg Mindfulness Inventory. 16 participants received a 5-day meditation training, focusing on body/breath awareness; the control group (N = 15) received no intervention. Measures were taken before the intervention and on 3 consecutive days after the training, with all participants receiving either no infusion, naloxone infusion, or saline infusion (blinded). Blood samples were taken in order to determine serum morphine and morphine glucuronide levels by applying liquid chromatography-tandem mass spectrometry analysis. Results: The meditation group produced fewer errors in ANT. Paradoxically, increases in pain tolerance occurred in both groups (accentuated in control), and correlated with reported mindfulness. Naloxone showed a trend to decrease pain tolerance in both groups. Plasma analyses revealed sporadic morphine and/or morphine metabolite findings with no discernable pattern. Discussion: Main objectives could not be verified. Since underlying study goals had not been made explicit to participants, on purpose (framing effects toward a hypothesized mindfulness-pain tolerance correlation were thus avoided, trainees had not been instructed how to 'use' mindfulness, regarding pain), the question remains open whether lack of meditation effects on pain tolerance was due to these intended 'non-placebo' conditions, cultural effects, or other confounders, or on an unsuitable paradigm. Conclusion: Higher pain tolerance through meditation could not be confirmed.

Pain Tolerance in Persons With Recognized and Unrecognized Myocardial Infarction: A Population-Based, Cross-Sectional Study

BACKGROUND

Unrecognized myocardial infarction (MI) is a prevalent condition associated with a similar risk of death as recognized MI. It is unknown why some persons experience MI with few or no symptoms; however, one possible explanation is attenuated pain sensitivity. To our knowledge, no previous study has examined the association between pain sensitivity and recognition of MI.

METHODS AND RESULTS

We conducted a population-based cross-sectional study with 4849 included participants who underwent the cold pressor test (a common experimental pain assay) and ECG. Unrecognized MI was present in 387 (8%) and recognized MI in 227 (4.7%) participants. Participants with unrecognized MI endured the cold pressor test significantly longer than participants with recognized MI (hazard ratio for aborting the cold pressor test, 0.64; CI, 0.47-0.88), adjusted for age and sex. The association was attenuated and borderline significant after multivariable adjustment. The association between unrecognized MI and lower pain sensitivity was stronger in women than in men, and statistically significant in women only, but interaction testing was not statistically significant (P for interaction=0.14).

CONCLUSIONS

Our findings suggest that persons who experience unrecognized MI have reduced pain sensitivity compared with persons who experience recognized MI. This may partially explain the lack of symptoms associated with unrecognized MI.

Exercise-induced hypoalgesia: Pain tolerance, preference and tolerance for exercise intensity, and physiological correlates following dynamic circuit resistance exercise

Previous research has demonstrated significant decreases in pain perception in healthy individuals following both aerobic and upper body resistance exercise, but research on circuit training has been limited. The purpose of the study was to determine the effects of a strenuous bout of dynamic circuit resistance exercise on pain threshold and pain tolerance in conjunction with changes in blood lactate levels, heart rate (HR), and perceived exertion. A sample of 24 college-age students participated in 2 sessions: (1) a maximal strength testing session and (2) a circuit training bout of exercise that consisted of 3 sets of 12 repetitions with a 1:1 work to rest ratio at 60% one-repetition maximum (1-RM) predicted from a three-repetition maximum (3-RM) for 9 exercises. Participants exhibited increases in pain tolerance, blood lactate levels, HR and perceived exertion following resistance exercise. Preference for exercise intensity was positively correlated with lactate post exercise and tolerance for exercise intensity was positively correlated with pain tolerance and lactate post exercise. In conclusion, this is the first study to demonstrate increases in pain tolerance following a dynamic circuit resistance exercise protocol and disposition for exercise intensity may influence lactate and pain responses to circuit resistance exercise.

Aerobic Exercise As a Potential Way to Improve Self-Control after Ego-Depletion in Healthy Female College Students

Purpose: To test whether aerobic exercise can help build self-control stamina in healthy female young adults. Stamina in this context is defined as the capability to endure ego depletion, which can be measured with a self-control task following another activity also requiring self-control.

Methods: Forty-five healthy undergraduate women were randomized to either an experimental group or control group. Participants in the experimental group were required to run in their campus running field for 30 min for a period of 5 weeks. Individuals in the control group were required to do diary entries regarding self-control in their daily lives, also for a period of 5 weeks. Before and after the 5-week intervention, participants completed a pain threshold test, a color word Stroop task and the following Cold Pressor Task (CPT) (with and without a distraction component).

Results: There was significant decrease of pain tolerance in session 2 relative to session 1 in the control group, but no such decline was found in the experimental group (though the improvement of pain tolerance was not significant), possibly suggesting successful self-control against this kind of decline.

Conclusions: Five weeks of aerobic exercise increased self-control after ego depletion in terms of pain tolerance. These findings suggest that aerobic exercise may serve as a potential effective intervention for enhancing self-control in a college female population.

Validation of simple and inexpensive algometry using sphygmomanometer cuff and neuromuscular junction monitor with standardized laboratory algometer

Background and Aims:

The availability, ergonomics and economics prohibit the routine use of algometers in clinical practice and research by the anesthesiologists. A simple bedside technique of quantitative pain measurement would enable the routine use of algometry. We proposed to validate simple pain provocation using sphygmomanometer cuff and the electric stimulation of neuromuscular junction monitor (TOF-guard, Organon Teknika) to measure pain against a standardized laboratory pressure algometer.

Material and Methods:

Pain detection threshold (Pdt) and pain tolerance threshold (Ptt) were measured in forty healthy volunteers of both genders, using the above three techniques. All measurements were repeated three times. The co-efficient of inter-rater reliability (or consistency) between three independent measurements obtained from each of the techniques was determined by Cronbach's co-efficient alpha (α C). The correlation between the mean Pdt and Ptt values recorded by standardized algometer and the sphygmomanometer technique and nerve stimulator technique was performed using Pearson Correlation. An r >0.5 and a two-tailed significance of <0.05 were considered as good correlation between the standardized algometer and the tested techniques.

Results:

There was a good inter-rater reliability (α C > 0.7) for the three techniques. There was a good correlation with r >0.65 (P < 0.001) between the measurements of standardized pressure algometer and the two techniques being tested as alternatives for algometer to measure pain.

Conclusion:

The sphygmomanometer cuff technique and electrical stimulation with the peripheral nerve stimulator to measure pain threshold and tolerance provide a simple, efficient, repeatable measure of pain intensity and can be used as suitable alternatives to standard algometers.

Sound can enhance the analgesic effect of virtual reality

Virtual reality (VR) technology may serve as an effective non-pharmacological analgesic to aid pain management. During VR distraction, the individual is immersed in a game presented through a head-mounted display (HMD). The technological level of the HMD can vary, as can the use of different input devices and the inclusion of sound. While more technologically advanced designs may lead to more effective pain management the specific roles of individual components within such systems are not yet fully understood. Here, the role of supplementary auditory information was explored owing to its particular ecological relevance. Healthy adult participants took part in a series of cold-pressor trials submerging their hand in cold water for as long as possible. Individual pain tolerances were measured according to the time (in seconds) before the participant withdrew their hand. The concurrent use of a VR game and the inclusion of sound was varied systematically within participants. In keeping with previous literature, the use of a VR game increased pain tolerance across conditions. Highest pain tolerance was recorded when participants were simultaneously exposed to both the VR game and supplementary sound. The simultaneous inclusion of sound may therefore play an important role when designing VR to manage pain.

General Theory versus ENA Theory: Comparing Their Predictive Accuracy and Scope

General theory attributes criminal behavior primarily to low self-control, whereas evolutionary neuroandrogenic (ENA) theory envisions criminality as being a crude form of status-striving promoted by high brain exposure to androgens. General theory predicts that self-control will be negatively correlated with risk-taking, while ENA theory implies that these two variables should actually be positively correlated. According to ENA theory, traits such as pain tolerance and muscularity will be positively associated with risk-taking and criminality while general theory makes no predictions concerning these relationships. Data from Malaysia and the United States are used to test 10 hypotheses derived from one or both of these theories. As predicted by both theories, risk-taking was positively correlated with criminality in both countries. However, contrary to general theory and consistent with ENA theory, the correlation between self-control and risk-taking was positive in both countries. General theory's prediction of an inverse correlation between low self-control and criminality was largely supported by the U.S. data but only weakly supported by the Malaysian data. ENA theory's predictions of positive correlations between pain tolerance, muscularity, and offending were largely confirmed. For the 10 hypotheses tested, ENA theory surpassed general theory in predictive scope and accuracy.

Childhood adversities and laboratory pain perception

Childhood adversity has frequently been related to a wide range of psychosomatic complaints in adulthood. The present study examined the relationship between different forms of childhood adversity and laboratory measures of pain. Heat pain tolerance and perceived heat pain intensity were measured in a community-based sample of 62 women (aged 20-64 years). Participants completed the Childhood Trauma Questionnaire (CTQ), which assesses five forms of childhood adversity: physical abuse, sexual abuse, emotional abuse, physical neglect, and emotional neglect. Somatic symptoms, depressive symptoms, and pain catastrophizing were assessed as potential mediators. Bivariate analyses indicated that emotional abuse but no other forms of childhood adversity were significantly related to decreased heat pain tolerance (r=-0.27; P<0.05). Accordingly, multiple regression analyses revealed that only emotional abuse was a significant predictor of heat pain tolerance (β=-0.62; P=0.034) when entering all CTQ subscales simultaneously. Although emotional abuse was also related to somatic symptoms, depressive symptoms, and pain catastrophizing, none of these variables mediated the relationship between childhood adversity and laboratory pain (P>0.1). No significant associations were found between any forms of childhood adversity and heat pain intensity. Our findings indicate that the severity of emotional childhood abuse is associated with decreased pain tolerance, an affective component of pain, but not with heat pain intensity, which has been described as a sensory component of pain.

Alterations in pain response are partially reversed by methylphenidate (Ritalin) in adults with attention deficit hyperactivity disorder (ADHD)

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is characterized by dysregulation of sensory processing and neurobiology of dopamine. Although cumulative evidence suggests that dopamine is involved in pain processing, pain perception in ADHD subjects and the effect of dopamine agonists such as methylphenidate (MP, Ritalin) on it have rarely been studied.

AIMS

The aims of this study were to (1) psychophysically assess sensitivity to pain in ADHD subjects as compared to controls and (2) examine the effects of MP on pain response in ADHD subjects.

METHODS

Thirty subjects with ADHD and 30 age- and gender-matched controls participated in a preliminary trial. Pain threshold, intensity, and tolerance in response to cold pain stimulation were measured for both groups (ADHD with no treatment). In addition, the ADHD group was reassessed following a single dose of MP treatment.

RESULTS

The ADHD subjects "without MP" in comparison with controls displayed significantly shorter cold pain threshold (2.8 ± 2.1 vs. 5.8 ± 2.5 seconds, respectively, P < 0.001) and cold tolerance (21.8 ± 22.3 vs. 62.8 ± 59.8 seconds, respectively P < 0.001). No differences in pain intensities between the groups were found. Following MP treatment, both cold threshold and tolerance in the ADHD subjects increased significantly compared to those with no treatment (3.6 ± 2.5 seconds, P = 0.011, and 46.4 ± 53.3 seconds, P < 0.001, respectively).

CONCLUSIONS

These results suggest that adults with ADHD are more sensitive to pain compared with controls and that MP may exert antinociceptive properties in these subjects. Randomized, controlled trials are warranted to verify these findings.

Insular cortex mediates increased pain tolerance in yoga practitioners

Yoga, an increasingly popular discipline among Westerners, is frequently used to improve painful conditions. We investigated possible neuroanatomical underpinnings of the beneficial effects of yoga using sensory testing and magnetic resonance imaging techniques. North American yogis tolerated pain more than twice as long as individually matched controls and had more gray matter (GM) in multiple brain regions. Across subjects, insular GM uniquely correlated with pain tolerance. Insular GM volume in yogis positively correlated with yoga experience, suggesting a causal relationship between yoga and insular size. Yogis also had increased left intrainsular white matter integrity, consistent with a strengthened insular integration of nociceptive input and parasympathetic autonomic regulation. Yogis, as opposed to controls, used cognitive strategies involving parasympathetic activation and interoceptive awareness to tolerate pain, which could have led to use-dependent hypertrophy of insular cortex. Together, these findings suggest that regular and long-term yoga practice improves pain tolerance in typical North Americans by teaching different ways to deal with sensory inputs and the potential emotional reactions attached to those inputs leading to a change in insular brain anatomy and connectivity.

Ultra-marathon runners are different: investigations into pain tolerance and personality traits of participants of the TransEurope FootRace 2009

INTRODUCTION

Susceptibility to pain varies among individuals and may predispose to a higher risk for pain disorders. Thus, it is of interest to investigate subjects who exhibit higher resistance to pain. We therefore tested pain tolerance and assessed personality traits of ultra-marathon athletes who are able to run 4487 km (2789 mi) over 64 days without resting days and compare the results to controls.

METHODS

After approval of the local ethics committee and with informed consent, 11 participants of the TransEurope FootRace (TEFR09 participants) and 11 matched (age, sex, and ethnicity) controls without marathon experience in the last 5 years were enrolled. They were tested for cold pain tolerance (cold pressor [CP] test), and the 240 item trait and character inventory (TCI) as well as the general self-efficacy (GSE) test were obtained.

RESULTS

TransEurope FootRace participants had a highly significant greater cold pain tolerance in the CP test than controls (P = 0.0002). While the GSE test showed no differences, the TCI test provided TEFR09 participants to be less cooperative and reward dependent but more spiritually transcendent than the controls. Significant positive correlations were found between the CP test pain score at 180 seconds and several TCI subscales showing that higher pain scores correlate with higher reward dependence, dependence, cooperativeness, empathy, and pure-hearted conscience.

CONCLUSIONS

Personality profiles as well as pain tolerance of our sample of TEFR09 participants differ from normal controls and-as obtained in previous studies-probably also from chronic pain patients. Low pain perception may predispose a person to become a long-distance runner. It remains unclear, however, whether low pain perception is cause or consequence of continuous extreme training.

The correlation of antepartum upper extremity cuff algometry with epidural analgesic requirements for labor

Background:

Individual parturients experience pain differently, and it is unknown how these differences affect their requirements for labor analgesics.

Materials and Methods:

Cuff algometry of the upper limb was used to determine the pain thresholds and temporal summation of pain scores in nulliparous women about to undergo induction of labor. Analgesia was provided, upon request, with a patient controlled epidural analgesia infusion of bupivacaine and fentanyl. Nurse-administered epidural boluses of bupivacaine or lidocaine were given for breakthrough pain. Partial Spearman correlations were used to correlate the cuff algometry measurements with the amount of analgesic medication required by the patient.

Results:

There was no significant correlation between any of the algometry measurements and the number of patient or nurse administered bupivacaine boluses. There was a correlation of 0.7 (P = 0.001) between the temporal summation scores and the hourly number of nurse-administered epidural lidocaine boluses; however, this was based on only 3 patients who required lidocaine boluses.

Conclusions:

The use of pre-labor cuff algometry of the upper limb does not correlate with the patient epidural analgesic requirements and subsequent analgesia administration.

The long-term prognosis of whiplash-associated disorders (WAD)

Somatic and mental symptoms in 22 patients (16 women and 6 men) 22-73 months after a whiplash injury are described. The results of the present study are compared with the corresponding results of a previous study on the same patients. According to the Quebec Classification System, the whiplash injuries of 15 patients were classified as grade 2 and those of 7 patients as grade 3. Pain intensity was evaluated by means of a visual analogue scale and muscular tenderness was assessed by pressure algometry. Algometry was also used to measure the pain tolerance level. The Mood Adjective Check List was used as a measure of mental well-being. During the 2 years that had passed since the previous study, the patients had improved regarding pain intensity, pain tolerance level and mental well-being. The results show that patients with prolonged disability after a whiplash injury can improve even after a long time.