The journal of pain : official journal of the American Pain Society
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Review Meta Analysis
Inhaled cannabis for chronic neuropathic pain: an individual patient data meta-analysis.
Chronic neuropathic pain, the most frequent condition affecting the peripheral nervous system, remains underdiagnosed and difficult to treat. Inhaled cannabis may alleviate chronic neuropathic pain. Our objective was to synthesize the evidence on the use of inhaled cannabis for chronic neuropathic pain. We performed a systematic review and a meta-analysis of individual patient data. We registered our protocol with PROSPERO CRD42011001182. We searched in Cochrane Central, PubMed, EMBASE, and AMED. We considered all randomized controlled trials investigating chronic painful neuropathy and comparing inhaled cannabis with placebo. We pooled treatment effects following a hierarchical random-effects Bayesian responder model for the population-averaged subject-specific effect. Our evidence synthesis of individual patient data from 178 participants with 405 observed responses in 5 randomized controlled trials following patients for days to weeks provides evidence that inhaled cannabis results in short-term reductions in chronic neuropathic pain for 1 in every 5 to 6 patients treated (number needed to treat = 5.6 with a Bayesian 95% credible interval ranging between 3.4 and 14). Our inferences were insensitive to model assumptions, priors, and parameter choices. We caution that the small number of studies and participants, the short follow-up, shortcomings in allocation concealment, and considerable attrition limit the conclusions that can be drawn from the review. The Bayes factor is 332, corresponding to a posterior probability of effect of 99.7%. ⋯ This novel Bayesian meta-analysis of individual patient data from 5 randomized trials suggests that inhaled cannabis may provide short-term relief for 1 in 5 to 6 patients with neuropathic pain. Pragmatic trials are needed to evaluate the long-term benefits and risks of this treatment.
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Vulvodynia is a prevalent vulvovaginal pain condition that disrupts the sexual and psychological health of affected women and their partners. Cross-sectional and daily experience studies suggest that partner responses to this pain influence the psychological and sexual sequelae of affected couples. However, their daily impact on pain and anxiety remain unknown. Using a daily diary method, 69 women (M age = 28.12, SD = 6.68) diagnosed with vulvodynia and their cohabiting partners (M age = 29.67, SD = 8.10) reported on male partner responses to women's pain and anxiety symptoms on sexual intercourse days (M = 6.54, SD = 4.99) over 8 weeks. Women also reported their pain during intercourse. Results indicated that women reported greater pain on days when they perceived higher solicitous and negative male partner responses, and on days when their male partner reported greater solicitous and lower facilitative responses. Women indicated higher anxiety symptoms on days when they perceived more negative male partner responses; men's anxiety symptoms were greater on days when they reported higher negative male partner responses. Targeting partner responses may enhance the quality and efficacy of interventions aimed at reducing pain in women with vulvodynia and couples' psychological distress. ⋯ This article examines the daily associations among male partner responses, women's pain during intercourse, and anxiety in couples coping with vulvodynia. Targeting male partner responses may enhance the quality of interventions aimed at reducing women's pain and the psychological distress of couples coping with vulvodynia.
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Randomized Controlled Trial Comparative Study
Comparing counterconditioning and extinction as methods to the reduce fear of movement-related pain.
Cognitive-behavioral treatments for chronic pain typically target pain-related fear; exposure in vivo is a common treatment focusing on disconfirming harm expectancy of feared movements. Exposure therapy is tailored on Pavlovian extinction; an alternative fear reduction technique that also alters stimulus valence is counterconditioning. We compared both procedures to reduce pain-related fear using a voluntary joystick movement paradigm. Participants were randomly allocated to the counterconditioning or extinction group. During fear acquisition, moving the joystick in 2 directions (conditioned stimulus [CS+]) was followed by a painful electrocutaneous stimulus (pain-unconditioned stimulus [US]), whereas moving the joystick in 2 other directions was not (CS-). During fear reduction, 1 CS+ was extinguished, but another CS+ was still followed by pain in the extinction group; in the counterconditioning group, 1 CS+ was extinguished and followed by a monetary reward-US, and another CS+ was followed by both USs (pain-US and reward-US). The results indicate that counterconditioning effectively reduces pain-related fear but that it does not produce deeper fear reduction than extinction. Adding a reward-US to a painful movement attenuated neither fear nor the intensity/unpleasantness of the pain. Both procedures changed stimulus valence. We contend that changing the affective valence of feared movements might improve fear reduction and may prevent relapse. ⋯ This article reports no immediate differences between counterconditioning and extinction in reducing pain-related fear in the laboratory. Unexpectedly, both methods also altered stimulus valence. However, we cautiously suggest that methods explicitly focusing on altering the affective valence of feared movements may improve the long-term effectiveness of fear reduction and prevent relapse.
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Humans are expert at recognizing facial features whether they are variable (emotions) or unchangeable (gender). Because of its huge communicative value, pain might be detected faster in faces than unchangeable features. Based on this assumption, we aimed to find a presentation time that enables subliminal discrimination of pain facial expression without permitting gender discrimination. For 80 individuals, we compared the time needed (50, 100, 150, or 200 milliseconds) to discriminate masked static pain faces among anger and neutral faces with the time needed to discriminate male from female faces. Whether these discriminations were associated with conscious reportability was tested with confidence measures on 40 other individuals. The results showed that, at 100 milliseconds, 75% of participants discriminated pain above chance level, whereas only 20% of participants discriminated the gender. Moreover, this pain discrimination appeared to be subliminal. This priority of pain over gender might exist because, even if pain faces are complex stimuli encoding both the sensory and the affective component of pain, they signal a danger. This supports the evolution theory relating to the necessity of quickly reading aversive emotions to ensure survival but might also be at the basis of altruistic behavior such as help and compassion. ⋯ This study shows that pain facial expression can be processed subliminally after brief presentation times, which might be helpful for critical emergency situations in clinical settings.
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Most, but not all, limb amputees develop phantom limb pain (PLP) or residual limb pain (RLP), and large interindividual differences in pain intensity and course are apparent. The present cross-sectional study of 122 double amputees investigated the possible role of genetic factors in PLP and RLP, assuming that strong individual predisposition results in high intraindividual concordance in pain phenotype. Intraindividual concordance was observed in 116 (95%) patients for development of PLP and in 110 patients (90%) for development of RLP. For both pain types, high intraindividual concordance was also observed for remission and current intensity. Moderate association for lifetime history and current intensity of PLP and RLP was observed both within and between limbs. The high intraindividual concordance in pain phenotypes suggests strong individual predisposition for PLP and RLP development. However, the finding of only moderate association between PLP and RLP suggests that susceptibility to these pain phenomena involves distinct, as well as common, risk factors. Genome-wide studies in large samples of single amputees may facilitate the dissection of these phenotypes and their underlying mechanisms. ⋯ The observation of high intraindividual concordance for PLP and RLP in 122 double amputees suggests that individual factors contribute to post-amputation pain. The relatively low intraindividual association between PLP and RLP suggests that these factors are at least partially specific for each pain type.