The journal of pain : official journal of the American Pain Society
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While it is generally accepted that women have lower pain thresholds for diverse forms of noxious stimuli, the mechanistic basis for this sexual dimorphism in nociceptive pain remains to be elucidated. We confirmed, in the rat, that females have lower cutaneous mechanical nociceptive thresholds and established a similar sexual dimorphism in muscle. To determine if a peripheral mechanism underlies this sexual dimorphism in pain threshold, we compared biophysical properties of cultured dorsal root ganglion (DRG) neurons that innervated the gastrocnemius muscle in female and male rats. DRG neurons from female rats, which innervated the gastrocnemius muscle, had a more hyperpolarized resting membrane potential. To determine if this was associated with a higher mechanical nociceptive threshold, in contradiction to our working hypothesis, we compared the function, in vivo, of nociceptive afferents innervating the gastrocnemius muscle in male and female rats. C-fiber nociceptors innervating muscle in female rats had higher mechanical thresholds than those in males. Other response characteristics of these nociceptors were not significantly different. Thus, both in vitro and in vivo electrophysiology experiments support the idea that lower mechanical nociceptive threshold in females may be due to sexual dimorphism in central nervous system mechanisms, a difference large enough to overcome an opposing difference in peripheral pain mechanisms. ⋯ This article unifies in vivo and in vitro electrophysiology with behavioral data examining the differences in mechanical nociceptive threshold between male and female rats. The data provide a novel perspective on the peripheral and behavioral outcomes of noxious mechanical stimulation.
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Randomized Controlled Trial
We discount the pain of others when pain has no medical explanation.
The present studies investigated the impact of medical and psychosocial information on the observer's estimations of pain, emotional responses, and behavioral tendencies toward another person in pain. Participants were recruited from the community (study 1: N = 39 women, 10 men; study 2: N = 41 women, 12 men) and viewed videos of 4 patients expressing pain, paired with vignettes describing absence or presence of 1) medical evidence for the pain and 2) psychosocial influences on the pain experience. A similar methodology was used for studies 1 and 2, except for the explicit manipulation of the presence/absence of psychosocial influences in study 2. For each patient video, participant estimations of each patient's pain and their own distress, sympathy, and inclination to help were assessed. In both studies, results indicated lower ratings on all measures when medical evidence for pain was absent. Overall, no effect of psychosocial influences was found, except in study 2 where participants indicated feeling less distress when psychosocial influences were present. The findings suggest that pain is taken less seriously when there is no medical evidence for the pain. The findings are discussed in terms of potential mechanisms underlying pain estimations as well as implications for caregiving behavior. ⋯ The present studies indicate that observers take the pain of others less seriously in the absence of clear medical evidence for the pain. These findings are important to further understand the social context in which pain for which there is no clear medical explanation is experienced.
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Study purposes were to determine the prevalence of persistent pain in the breast; characterize distinct persistent pain classes using growth mixture modeling; and evaluate for differences among these pain classes in demographic, preoperative, intraoperative, and postoperative characteristics. In addition, differences in the severity of common symptoms and quality of life outcomes measured prior to surgery, among the pain classes, were evaluated. Patients (n = 398) were recruited prior to surgery and followed for 6 months. Using growth mixture modeling, patients were classified into no (31.7%), mild (43.4%), moderate (13.3%), and severe (11.6%) pain groups based on ratings of worst breast pain. Differences in a number of demographic, preoperative, intraoperative, and postoperative characteristics differentiated among the pain classes. In addition, patients in the moderate and severe pain classes reported higher preoperative levels of depression, anxiety, and sleep disturbance than the no pain class. Findings suggest that approximately 25% of women experience significant and persistent levels of breast pain in the first 6 months following breast cancer surgery. ⋯ Persistent pain is a significant problem for 25% of women following surgery for breast cancer. Severe breast pain is associated with clinically meaningful decrements in functional status and quality of life.
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The recently revised version of the Short-Form McGill Pain Questionnaire (SF-MPQ-2) was created to assess both neuropathic and non-neuropathic pain. The current study extends prior research by testing the reliability and validity of the SF-MPQ-2 in a sample of U.S. veteran patients with a range of chronic pain diagnoses. Participants (N = 186) completed the SF-MPQ-2, a sociodemographic questionnaire, the Structured Clinical Interview for the DSM-IV, and self-report pain and psychiatric measures. Pain diagnoses were extracted from the electronic medical record. The SF-MPQ-2 total and scale scores demonstrated good-to-excellent internal consistency. Convergent and discriminant validity were supported, and SF-MPQ-2 total and scale scores increased with number of pain diagnoses and pain severity. Confirmatory factor analyses indicated that a 4-factor model fit the data better than a single-factor model. However, high intercorrelations among the 4 latent constructs were observed, and a second-order global pain construct also emerged. Overall, the SF-MPQ-2 demonstrated excellent reliability and validity in a sample of U.S. veteran patients with chronic neuropathic and non-neuropathic pain. Future psychometric studies of the SF-MPQ-2 should employ longitudinal data to evaluate the ability of scale scores to uniquely predict clinical and health service outcomes. ⋯ This article presents the psychometric properties of a revised version of the SF-MPQ-2. This measure may have great utility as a screening tool in clinical practice and as an outcome measure in clinical trials.
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Recent research has implicated pain-related fear in relation to functional outcomes in children with chronic pain. The current study examined fear of pain, disability, and depression within the context of an intensive pain rehabilitation program. One hundred forty-five children and adolescents who participated in an intensive interdisciplinary pediatric pain rehabilitation day program were assessed in this study. Patients completed measures of pain intensity, pain-related fears, functional disability, and depressive symptoms at admission, discharge, and on average, 2 months postdischarge. After controlling for pain intensity, pain-related fear was significantly related to disability and depressive symptoms at all time points. As predicted, a decline in pain-related fear was significantly associated with a decrease in disability and depressive symptoms. Interestingly, high levels of pain-related fears at admission predicted less reduction in functional disability and depression at discharge, suggesting that high levels of pain-related fear may be a risk factor in relation to treatment outcomes. Overall, results indicate that the relationship between fear of pain and changes in disability and depressive symptoms are closely linked, with fear of pain playing an important role in treatment. ⋯ This paper presents results underscoring the importance of pain-related fear in relation to treatment response for children and adolescents with chronic pain. These findings support the need to develop and implement interventions that target reductions in pain-related fear.