Biomedical subjects

Michael E Robinson

Publications and source records attributed to Michael E Robinson.

At least 37 records · Page 2Linked to original sources

PubMed2005

Effect of eccentric strength testing on delayed-onset muscle pain.

This investigation was designed to determine the effect of eccentric strength testing on delayed-onset muscle pain in 20 untrained university students. Initially, eccentric strength testing (5-repetition maximum [5RM]) was performed bilaterally. Next, 1 arm completed 3 sets of 10 eccentric repetitions to induce delayed-onset muscle pain. Then, in a subsequent session, whichever arm previously performed only the 5RM test completed the 5RM test a second time and the 3 sets of 10 eccentric repetitions. Statistical analyses supported significantly increased pain intensity and unpleasantness across 48 hours post-5RM test alone. However, pain intensity and unpleasantness after the eccentric training bouts were significantly lower in the arm that performed 2 5RM tests than the arm that performed only 1. Thus, the eccentric strength testing produced delayed-onset muscle pain and protected against future delayed-onset muscle pain. These effects should be considered when such testing is used in baseline strength assessments.

Adult↗

PubMed2005

Fatigue in systemic lupus erythematosus: contributions of disease activity, pain, depression, and perceived social support.

OBJECTIVE: Pain and psychological distress are associated with fatigue, and social support may play a buffering role in the adjustment to a chronic disease. Investigations of the relationship between fatigue and disease activity in chronic diseases have provided inconclusive findings. The influence of medications on perceived fatigue remains unclear. We investigated the relationship between pain, depression, fatigue, and disease activity in patients with systemic lupus erythematosus (SLE). METHODS: Participants (n = 127) completed a psychosocial questionnaire during routine clinic visits. Hierarchical multiple regression analysis was conducted to predict the contribution of disease activity, pain, depression (Beck Depression Inventory), and perceived social support to fatigue. RESULTS: Disease activity as measured by SLE Disease Activity Index (SLEDAI) did not significantly predict self-reported levels of fatigue. Medication usage did not predict fatigue levels. Pain and depression were both unique positive predictors of fatigue. Controlling for pain and depression, perceived social support contributed negatively to the variance in fatigue scores, suggesting a buffering effect. This model reliably explained 42% of the variance in fatigue scores. CONCLUSION: Our results emphasize the importance of depression, pain, and perceived social support in predicting reported fatigue levels in patients with SLE. In contrast, disease activity measured by SLEDAI does not appear to account for fatigue in SLE. Understanding the effect of psychosocial factors on fatigue in SLE may improve patient outcomes through psychosocial interventions aimed at reducing pain and increasing coping skills and social support.

Age Distribution↗

PubMed2004

Representations of pain in the brain.

In this paper, the relationships between neural mechanisms of persistent pain and the neural representations of these conditions in the human and animal brain will be reviewed. Animal models of chronic pain, such as the sciatic nerve constrictive injuries, are accompanied by somatotopically organized increases in several pain-related areas of the brain. Recent human brain imaging studies utilizing functional magnetic resonance imaging and positron emission tomography have elucidated the cerebral representations of visceral and somatic hypersensitivity. Both forms of hypersensitivity are represented in similar brain regions that are activated during acute pain, yet have a more extensive or intense cerebral representation. This suggests that these somatic and visceral hyperalgesic states may be represented by increased activity in the same cerebral pathways and centers that are involved in nociceptive stimuli in normal individuals. Hyperalgesic states during clinically relevant pain are especially reflected in brain areas such as the anterior cingulate and prefrontal cortical regions.

Afferent Pathways↗

PubMed2004

Sex differences in pain anchors revisited: further investigation of "most intense" and common pain events.

Recent research suggests that the interpretation of maximal endpoints of pain scales vary between sexes. The purposes of this study were to investigate sex differences in (a) maximal endpoints of pain scales and (b) bias, discrimination, and the "better than average effect" for ratings of common pain events. Study participants described and rated the intensity of events that were the "most intense pain imaginable" for the typical woman, typical man, and one's self. Study participants also described and rated the intensity of the "most painful" events they had experienced. Study participants completed the situational pain questionnaire (SPQ), which measured the amount of pain that the typical woman, typical man, or one's self would be expected to experience during thirty common painful events. One hundred and fifteen undergraduate psychology students completed this study. Men and women differed in the categories of events selected for most intense pain imaginable for one's self. There were no significant sex differences for the intensity of most intense self-imagined pain or most painful event experienced. However, women were more likely to report the intensity of their worst self-imagined pain event as 100/100. In addition, only women demonstrated a significant correlation between the intensity of most painful self-experienced event and intensity of most intense self-imagined event. Analyses of the SPQ discrimination scores revealed no sex or version differences. Analyses of the SPQ bias scores showed that both sexes indicated that the typical woman would rate the intensity of common pain events higher than would the typical man. Women rated the intensity of common pain events for themselves lower than for the typical woman, but higher than the typical man, and men rated also rated themselves as lower than the typical women, but the same as the typical man. Thus, there was inconsistent support for the "better than average effect". Future research is needed to determine the clinical relevance of sex differences in pain anchors and gender-related stereotypes for evaluating other people's pain.

Adolescent↗

PubMed2004

Influences of gender role and anxiety on sex differences in temporal summation of pain.

UNLABELLED: Previous research has consistently shown moderate to large differences between pain reports of men and women undergoing experimental pain testing. These differences have been shown for a variety of types of stimulation. However, only recently have sex differences been demonstrated for temporal summation of second pain. This study examined sex differences in response to temporal summation of second pain elicited by thermal stimulation of the skin. The relative influences of state anxiety and gender role expectations on temporal summation were investigated. Asymptomatic undergraduates (37 women and 30 men) underwent thermal testing of the thenar surface of the hand in a temporal summation protocol. Our results replicated those of Fillingim et al indicating that women showed increased temporal summation compared to men. We extended those findings to demonstrate that temporal summation is influenced by anxiety and gender role stereotypes about pain responding. When anxiety and gender role stereotypes are taken into account, sex is no longer a significant predictor of temporal summation. These findings highlight the contribution of social learning factors in the differences between sexes' pain perception. PERSPECTIVE: Results of this study demonstrate that psychosocial variables influence pain mechanisms. Temporal summation was related to gender role expectations of pain and anxiety. These variables explain a significant portion of the differences between men and women's pain processing, and may be related to differences in clinical presentation.

Adolescent↗

PubMed2004

Prior pain experience: influence on the observation of experimental pain in men and women.

UNLABELLED: Research examining perceptions of subjects participating in an experimental pain task has not been widely studied. The primary purpose of this study was to examine the influence of prior experience with the cold pressor on subsequent perceptions of others experiencing this same pain task. Furthermore, to replicate our previous work, we examined how individuals observe experimentally induced pain in male and female participants. Possible interactions between order of cold pressor experience, sex of the viewer, sex of the individual being observed, and characteristics attributed to the individuals in the videos were also analyzed. The sample was composed of 57 participants. They were each randomized to 1 of 2 conditions: (1) participate in cold pressor task before viewing a presentation of 10 video clips (of subjects in cold pressor task), rate videos, and complete battery of questionnaires or (2) cold pressor participation after completion of the same questionnaires, and viewing/rating videos. Participants viewing the videos provided ratings including observed pain and emotional characteristics they attributed to the individuals. These results replicated and extended our previous work by demonstrating a gender bias (ie, a stereotypical belief about an individual on the basis of their sex) in the observation of pain, such that participants rated female subjects as experiencing greater pain intensity when undergoing a cold pressor task compared to male subjects. Furthermore, experiencing the cold pressor before watching the videos increased a participant's pain ratings of observed pain. There were also several significant interactions between cold pressor condition, sex of video participant, sex of viewer, and emotional/behavioral characteristics attributed to the video participant. PERSPECTIVE: Results of this study demonstrate that prior experience with pain increases accuracy of estimating others' pain. Gender role expectations also influence observer's ratings of pain, and prior experience of pain influences men and women differently.

Adolescent↗

PubMed2004

Body pain area and pain-related negative affect predict clinical pain intensity in patients with fibromyalgia.

UNLABELLED: Patients with fibromyalgia (FM) report widespread chronic musculoskeletal pain. Palpation of 9 paired tender points (TPs) is commonly used for the diagnosis of FM according to criteria specified by the American College of Rheumatology. Although TP palpation can be used to assess deep tissue hypersensitivity, it has failed as a reliable indicator of clinical pain intensity in FM. The sum of local areas of pain (SLAP) obtained from a body pain diagram represents a relevant measure of the spatial extent of clinical pain, a feature most likely important for FM pain. Because spatial summation of pain can be an important determinant of clinical pain intensity, we hypothesized that this measure would predict clinical pain intensity in FM patients. Because pain is strongly associated with negative emotions, we evaluated the relationship of pain-related negative affect (PRNA) with clinical pain intensity in FM. The independent contributions of SLAP, PRNA, and TP count to the variance of clinical pain intensity were assessed in 280 FM patients. Clinical pain intensity of 280 FM patients was measured by using a visual analogue scale. FM patients shaded all painful body areas on body pain diagrams. Dolorimetry was used for TP evaluations. PRNA was assessed with the Medical College of Virginia Pain Questionnaire. Hierarchical linear regression was used to test the association of SLAP, TPs, and PRNA with clinical pain intensity. FM patients' mean visual analogue scale rating (0 to 100) of usual clinical pain was 50.1. Mean SLAP, TP count, and PRNA were 11.4, 16.0, and 44.3, respectively. Hierarchical linear regression analysis identified SLAP, TP count, and PRNA as independent predictors of clinical pain that accounted for 45% of the variance in clinical pain intensity ratings in FM patients. Consistent with the literature, TP count predicted only a small part (4%) of this variance. Our statistical model of body pain areas and negative affect predicts a large portion of the variance of pain intensity in FM. This result suggests that the extent of pain areas and negative emotions are uniquely associated with clinical pain intensity in FM. PERSPECTIVE: The number of painful body areas obtained by body pain diagrams is a better predictor of clinical pain intensity than TPs in FM patients. The combination of painful body areas, TP counts, and PRNA predicts 45% of the clinical pain intensity of FM patients. This finding might be useful for clinical evaluations of FM patients.

Adult↗

PubMed2004

Self-care behaviors for muscle pain.

UNLABELLED: This investigation examined self-care behaviors for muscle pain because of the prevalence of musculoskeletal pain and the substitution of self-care for formal medical care. In Study 1, university students (N = 187) completed a retrospective questionnaire about self-care for muscle pain. In Study 2, muscle pain was experimentally induced in university students (N = 79) with subsequent measurement of self-care. In both studies, stretching and massaging were the most frequently performed behaviors, and consuming medication was the least frequently performed. In Study 1, the perceived effectiveness of behaviors and level of pain required to perform self-care accounted for 12% to 32% of the variance in behavior frequency. In Study 2, pain ratings and pain during activities were higher among those who performed self-care (ds = .59 to 1.00). These studies indicated that self-care behaviors are performed for both naturally occurring and experimentally induced muscle pain. However, both studies determined that the performance of self-care behaviors did not always correspond with current evidence of treatment effectiveness for muscle injuries. Unique opportunities for future investigations of self-care behavior models and interventions are permitted by muscle pain induction. PERSPECTIVE: Self-care for pain reduction is an understudied behavior. This report describes 2 studies of self-care behaviors for naturally occurring and experimentally induced muscle pain. The most frequent types of self-care behaviors are similar for the types of pain, and the perceived effectiveness of behaviors and pain level influence performance of the behaviors.

Adult↗

PubMed2004

Maintenance of windup of second pain requires less frequent stimulation in fibromyalgia patients compared to normal controls.

Many chronic pain syndromes, including fibromyalgia (FM), show evidence of central nervous system hyperexcitability related to central sensitization. Windup (WU) of second pain reflects increased excitability of spinal cord neurons that is related to central sensitization. Psychophysical testing can help characterize this important central nervous system phenomenon because of the parallels between electrophysiological WU and WU of second pain. Animal experiments have shown that once WU has been established, only low frequency tonic nociceptive input is required to maintain the sensitized state of dorsal horn neurons (WU-maintenance or WU-M). The stimulus frequency necessary to maintain the hyperexcitability of spinal cord neurons can provide a measure of central sensitization. Because central sensitization plays an important role in many chronic pain syndromes including FM, we compared WU-M in 72 normal controls (NC) and 104 FM subjects. WU of second pain was produced by a train of 0.7 s duration thermal pulses applied to the glabrous surface of the hands at a frequency of 0.3 Hz. Enhanced second pain associated with WU could, thereafter, be maintained in FM but not NC subjects for up to 120 s by stimuli delivered at 0.16 and 0.08 Hz (WU-M stimuli). These two frequencies of stimulation do not produce WU when delivered alone. Thus, unlike NC subjects, FM subjects showed enhanced second pain during WU-M stimuli at very low stimulus frequencies, indicating central sensitization. Increased WU sensitivity, enhanced WU-M, and increased WU-related aftersensations help account for persistent pain conditions in FM subjects. In addition to WU, WU-M appears to be a useful tool to study mechanisms of pain in patients with characteristics of central sensitization.

Adult↗

PubMed2004

Spatial summation of heat pain within and across dermatomes in fibromyalgia patients and pain-free subjects.

The mechanisms of spatial summation of pain (SSP) include pain coding dependent on impulse frequency and the number of recruited central neurons. However, SSP may also be influenced by pain inhibitory mechanisms, such as diffuse noxious inhibitory controls. Abnormal interactions between pain inhibitory mechanisms and SSP may be relevant for chronic pain conditions such as fibromyalgia (FM) and may help explain why widespread pain is characteristic for this chronic pain syndrome. The present study was designed to determine the difference of thermal SSP in the upper extremities between FM and normal control (NC) subjects, particularly within and across dermatomes of the hand. Fourteen NC and 19 FM subjects were enrolled in this study. SSP testing sessions involved immersion of each individual fingertip as well as stepwise immersion of the fingers, hands, and forearms in a hot water bath (46 degrees Celsius) for 5s and 20s. In addition, immersion of several fingertips across dermatome C(7)-C(8) was compared to progressive immersion of the index finger (dermatome C(7)). These experiments demonstrated significant spatial summation of heat-induced pain in both FM and NC subjects. SSP was most extensive within the fingers, and became negligible as the stimulus area increased above the hand. Furthermore, SSP was more pronounced within one dermatome such as that of the index finger than across several dermatomes of the hand. These results were similar for both FM and NC subjects. Thus, mechanisms of SSP, including possible inhibitory factors that limit this relevant pain mechanism, appear to be similar for both FM and NC subjects.

Adult↗

PubMed2004

Autonomic dysfunction and gastroparesis in cirrhosis.

BACKGROUND: Patients with cirrhosis of the liver frequently present with many gastrointestinal complaints that are most likely due to abnormal gastrointestinal motility. The cause of these motility disorders in cirrhotics is unknown, however, underlying autonomic dysfunction may play a role. OBJECTIVE: To determine the association between autonomic dysfunction and delayed gastric emptying in cirrhotic patients. METHODS: We prospectively studied 20 patients with cirrhosis of the liver and postprandial abdominal pain, nausea, and vomiting and 10 asymptomatic patients with Hepatitis C (HCV) and no evidence of cirrhosis. All patients underwent 5 standardized cardiovascular tests to assess autonomic function. Each test was scored on a continuum from 0 (normal) to 5 (severe disease), thus producing a composite score of 0 to 5 for each subject. A composite score of greater than 1.5 was considered abnormal, with 5 representing severe autonomic involvement. A solid phase gastric emptying study was performed in each patient and a gastric retention of greater than 50% at 100 minutes was considered abnormal. RESULTS: The mean percent retention at 100 minutes was 70.7% in the cirrhotic group vs. 26.1% (P < 0.001) in the patients with HCV and no evidence of cirrhosis (controls). The composite autonomic score for the cirrhotic group was 3.4 vs. 1.2 (P < 0.001) in the controls. CONCLUSIONS: Our results suggest that gastroparesis is common in patients with cirrhosis of the liver, and may account for gastrointestinal symptoms of postprandial abdominal pain, nausea, and vomiting. The presence of autonomic dysfunction correlates positively with underlying motility disorders, such as delayed gastric emptying.

Adult↗

PubMed2004

Compliance in pain rehabilitation: patient and provider perspectives.

OBJECTIVE: To identify potential predictors and correlates of compliance and to examine differences between patient and provider perspectives on compliance. PATIENTS: One hundred eighty-four patients (84 men and 96 women) were recruited from a chronic pain treatment program for this telephone follow-up study. RESULTS: Health care providers (HCPs) reported making more recommendations than patients reported hearing. Patients rated themselves as more compliant than did HCPs. Overall compliance rates at a >6-month follow-up were 89% from the patients' perspective and 70% from the HCPs' perspective. HCPs rated compliance specific to psychological care as more related to positive outcomes than did patients. Participants' pain and anxiety ratings at a >6-month follow-up and satisfaction with treatment were significantly associated with patients' compliance ratings. For HCP-rated compliance, only HCPs' perceived benefit and interference from compliance were associated. CONCLUSION: Results suggest important disparities between HCPs and patients on remembered recommendations, levels of compliance, and health-related importance of complying with recommendations.

Adult↗

PubMed2003

Diffuse noxious inhibitory controls (DNIC) attenuate temporal summation of second pain in normal males but not in normal females or fibromyalgia patients.

Diffuse noxious inhibitory control (DNIC) is part of a central pain modulatory system that relies on spinal and supraspinal mechanisms. Previous studies have shown that fibromyalgia (FMS) patients are lacking DNIC effects on experimental pain, compared to normal control (NC) subjects. Because DNIC has a greater effect on second pain than on first pain, we hypothesized that wind-up (WU) of second pain should be attenuated by a strong conditioning stimulus. Thus, we compared DNIC's effect on WU in three groups of subjects: 11 NC males, 22 NC females, and 11 FMS females. To separately assess the contributions of distraction related mechanisms to inhibition of second pain, we designed the experiment in such a way that directed the subjects' attention to either the test or conditioning stimulus. Repeated heat taps to the thenar surface of the right hand were used as test stimuli to generate WU of second pain. Immersion of the left hand into a hot water bath was the conditioning stimulus. As previous experiments have shown, DNIC requires a strong conditioning stimulus for pain attenuation, which may be at least partly dependent on a distraction effect. DNIC significantly inhibited thermal WU pain in normal male subjects, but adding distraction to the DNIC effect did not increase the extent of this inhibition. In contrast, neither DNIC nor DNIC plus distraction attenuated thermal WU pain in female NCs. DNIC plus distraction but not DNIC alone produced significant inhibition of thermal WU pain in female FMS patients. Our results indicate that DNIC effects on experimental WU of second pain are gender specific, with women generally lacking this pain-inhibitory mechanism.

Adult↗

PubMed2003

Visceral and cutaneous hypersensitivity in Persian Gulf war veterans with chronic gastrointestinal symptoms.

Approximately 697000 United States military personnel participated in the Persian Gulf War (PGW) between August 1990 and March 1991. By April 1997, over 25% of veterans reported chronic health complaints of underdetermined etiology. Gastrointestinal symptoms were among the most frequently reported symptoms including abdominal pain and diarrhea. The objectives of this study were (1). to determine if PGW veterans chronic abdominal pain and diarrhea exhibit visceral and cutaneous hypersensitivity, (2). to determine if these differences in pain sensitivity are significantly associated with psychological stress. A total of 12 veterans (ten males, two females) (39+/-9 years) who were deployed to the Persian Gulf were enrolled. Seven civilians without prior military experience (five males, two females) and five veterans (five males) who had previously been deployed for active combat were enrolled as controls (35+/-9 years). All 12 PGW veterans reported chronic abdominal pain and diarrhea (negative diagnostic workup) that developed during their tour of duty in the Persian Gulf region. All patients completed a battery of psychological assessments and then randomly received experimental visceral (rectal distension of 35 and 55 mmHg for 30s) and cutaneous (immersion of right foot in 45 and 47 degrees C water for 30s) pain stimuli after which they rated their pain intensity and pain unpleasantness on a continuous visual analogue scale (M-VAS) scale. The trials were repeated and the mean M-VAS scores for the two trials were recorded for each subject. In comparison to controls, PGW subjects reported statistically significant higher mean ratings of pain intensity and pain unpleasantness in response to 35 and 55 mmHg rectal distention (P<0.001) and in response to 45 and 47 degrees C water immersion (P<0.001) of the hand and foot. Results of the hierarchical regressions indicated that the psychological measures (i.e. anxiety, somatic focus) accounted for a significant amount of variance in each of the pain measures. PGW veterans who developed chronic abdominal pain and diarrhea during their tour of duty exhibit visceral hypersensitivity similar to patients with the irritable bowel syndrome. These veterans also have cutaneous hypersensitivity and higher levels of anxiety and somatic focus accounting for these differences in pain reporting.

Adult↗

PubMed2003

Temporal summation of pain from mechanical stimulation of muscle tissue in normal controls and subjects with fibromyalgia syndrome.

Individuals diagnosed with fibromyalgia syndrome (FMS) report chronic pain that is frequently worsened by physical activity and improved by rest. Palpation of muscle and tendinous structures suggests that nociceptors in deep tissues are abnormally sensitive in FMS, but methods of controlled mechanical stimulation of muscles are needed to better characterize the sensitivity of deep tissues. Accordingly, force-controlled mechanical stimulation was applied to the flexor digitorum muscle of the forearm in a series of brief contacts (15 stimuli, each of 1s duration, at 3 or 5s interstimulus intervals). Repetitive stimulation was utilized to determine whether temporal summation of deep muscular pain would occur for normal subjects and would be enhanced for FMS subjects. Moderate temporal summation of deep pain was observed for normal controls (NC), and temporal summation was greatly exaggerated for FMS subjects. Temporal summation for FMS subjects occurred at substantially lower forces and at a lower frequency of stimulation. Furthermore, painful after-sensations were greater in amplitude and more prolonged for FMS subjects. These observations complement a previous demonstration that temporal summation of pain and after-sensations elicited by thermal stimulation of the skin are moderately enhanced for FMS subjects. Abnormal input from muscle nociceptors appears to underlie production of central sensitization in FMS that generalizes to input from cutaneous nociceptors.

Adult↗

PubMed2003

Central representation of visceral and cutaneous hypersensitivity in the irritable bowel syndrome.

We have previously shown that irritable bowel syndrome (IBS) patients have both visceral and cutaneous hyperalgesia. The neural mechanisms of these forms of hyperalgesia were further characterized by comparing cortical processing of both rectal distension (35, 55mmHg) and cutaneous heat nociceptive stimuli (foot immersion in 45 and 47 degrees C water bath) in IBS patients and in a group of healthy age/sex-matched controls. Our approach relied on functional magnetic resonance imaging neuroimaging analyses in which brain activation in age/sex-matched control subjects was subtracted from that found in IBS patients. These analyses revealed that both rectal distension and cutaneous heat stimuli evoked greater neural activity in several brain regions of IBS patients in comparison to age/sex-matched control subjects. These include those related to early stages of somatosensory processing (e.g. thalamus, somatosensory cortex) as well as those more related to cognitive and affective processing (insular, anterior cingulate, posterior cingulate, prefrontal cortex). Thus, our results support the hypothesis that hyperalgesia of IBS is manifested by increased somatosensory processing at all cortical levels. This was found to be the case not only for visceral hyperalgesia but also for cutaneous heat hyperalgesia, a likely form of secondary hyperalgesia. Furthermore, visceral and heat hyperalgesia were accompanied by increased neural activity within the same brain structures. These results support the hypothesis that visceral and cutaneous hyperalgesia in IBS patients is related to increased afferent processing in pathways ascending to the brain rather than to selectively increased activity at higher cortical levels (e.g. limbic and frontal cortical areas).

Adult↗

PubMed2003

Gender bias in the observation of experimental pain.

The aim of this study was to examine how men and women observe experimentally induced pain in male and female participants and to specifically determine the accuracy of observed pain ratings, the possible interactions between the sex of the viewer and the sex of the individual being observed, and the influence of gender role expectations on observed pain ratings. The sample comprised 29 participants (15 females). They each completed a battery of psychological questionnaires and viewed a presentation of 10 randomly ordered video clips. Each presentation consisted of 10 video clips, lasting 30s, of a participant (five males and five females) in the cold pressor task. The participants viewing the videos were asked to provide several ratings, including observed pain intensity and gender role related characteristics of the individual in the video. In terms of sex of the video participant, results indicated that viewers rated male videos as having less pain than female videos although the effect was small. Regarding sex of the viewer, results indicated that for both male and female videos, female viewers rated observed pain intensity significantly higher than did male viewers. In terms of accuracy, results indicated that on average, female video participants' pain was underestimated by 14 points, while male videos participants' pain was underestimated by 22 points (on a 0-100-point scale). Pain intensity ratings and pain tolerance from the participants in the videos did not differ significantly with respect to sex, though women had shorter tolerance times and higher pain ratings than men. Hierarchical regression analyses indicated that expectations of gender related 'endurance of pain' significantly predicted ratings of both male and female videos. When endurance expectations were controlled, sex of the viewer no longer significantly predicted observed pain ratings. The 'willingness to report pain' variable was not a significant predictor of observed pain ratings. Our results show that women are perceived to have more pain than men, that there was a tendency by both sexes to underestimate pain in others, but men showed even greater underestimation, and that gender role expectations of pain endurance given by the video observers accounted for substantial variance in their ratings of pain in the videos.

Adolescent↗

PubMed2003

The contributions of suggestion, desire, and expectation to placebo effects in irritable bowel syndrome patients. An empirical investigation.

In order to investigate external factors that may influence the magnitude of placebo analgesia as well as psychological factors that mediate placebo analgesia, 13 irritable bowl syndrome (IBS) patients rated evoked rectal distension and cutaneous heat pain under the conditions of natural history (NH), rectal placebo (RP), rectal nocebo (RN), rectal lidocaine (RL) and oral lidocaine (OL). Patients were given verbal suggestions for pain relief and rated expected pain levels and desire for pain relief for both evoked visceral and cutaneous pain, respectively. Large reductions in pain intensity and pain unpleasantness ratings were found in the RP, RL and OL condition as compared to the natural history condition, whereas no significant difference in pain reduction between the three treatment conditions was found. Ratings during RN and NH were not statistically different. Compared to a previous study, which shows that rectal lidocaine reverses visceral and cutaneous hyperalgesia, these results suggest that adding a verbal suggestion for pain relief can increase the magnitude of placebo analgesia to that of an active agent. Since IBS patients rate these stimuli as much higher than do normal control subjects and since placebo effects were very large, they probably reflect anti-hyperalgesic mechanisms to a major extent. Expected pain levels and desire for pain relief accounted for large amounts of the variance in visceral pain intensity in the RP, RL, and OL condition (up to 81%), and for lower amounts of the variance in cutaneous pain intensity. Hence, the combination of expected pain levels and desire for pain relief may offer an alternative means of assessing the contribution of placebo factors during analgesia.

Administration, Oral↗