Pain
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Meta Analysis
A systematic review with meta-analyses of the association between stigma and chronic pain outcomes.
Stigma is common in people experiencing chronic pain and there are indications that it may adversely affect pain outcomes. However, to date, there is no systematic review exploring the impact of stigma on chronic pain-related outcomes. This systematic review and meta-analysis aimed to examine the association between stigma and key chronic pain outcomes and differences in stigma between pain conditions. ⋯ Data from 2 prospective studies and those only reporting multivariate analyses that were not included in meta-analyses further supported these findings. There was some evidence that individuals who experience pain conditions with less clear pathophysiology may report greater stigma, although more research is needed. The review highlights that there is a growing number of studies on stigma in the pain field showing an adverse association between stigma and chronic pain outcomes.
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Although multisite pain can markedly reduce work ability, the relevance of the bodily pain distribution as a predictor of long-term sick leave is still unknown. This study aimed to investigate the association between musculoskeletal pain distributions and long-term sick leave in the general working population of Denmark and included 66,177 currently employed wage earners without long-term sick leave during the prior 52 weeks. Participants reported whether they had pain in the lower extremity (hips/knees), upper extremity (neck/shoulders), or the low back. ⋯ Workers reporting pain in all 3 regions experienced a 72% increased risk (HR [95% CI]: 1.72 [1.55-1.91]). Thus, the number of pain regions seems to matter more than the exact pain location. The spatial extension of musculoskeletal pain in workers functions as a gradient system, where pain spread throughout the body is an independent indicator of the high risk of long-term sick leave.
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The rostral ventromedial medulla (RVM) is a crucial structure in the descending pain modulatory system, playing a key role as a relay for both the facilitation and inhibition of pain. The chronic social defeat stress (CSDS) model has been widely used to study stress-induced behavioral impairments associated with depression in rodents. Several studies suggest that CSDS also causes changes related to chronic pain. ⋯ In addition, RVM inhibition in animals exposed to a subthreshold social defeat stress protocol induces a susceptible phenotype, facilitating all stress outcomes. Finally, chronic RVM inhibition-without any social stress stimulus-induces chronic pain but not depressive-like behaviors. Our findings provide insights into the comorbidity between chronic pain and depression by indicating the involvement of the RVM in establishing social stress-induced behavioral responses associated with both chronic pain and depression.
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Meta Analysis
The effect of unpredictability on the perception of pain: a systematic review and meta-analysis.
Despite being widely assumed, the worsening impact of unpredictability on pain perception remains unclear because of conflicting empirical evidence, and a lack of systematic integration of past research findings. To fill this gap, we conducted a systematic review and meta-analysis focusing on the effect of unpredictability on pain perception. We also conducted meta-regression analyses to examine the moderating effect of several moderators associated with pain and unpredictability: stimulus duration, calibrated stimulus pain intensity, pain intensity expectation, controllability, anticipation delay, state and trait negative affectivity, sex/gender and age of the participants, type of unpredictability (intensity, onset, duration, location), and method of pain induction (thermal, electrical, mechanical pressure, mechanical distention). ⋯ However, several significant moderators were found, ie, targeted stimulus pain intensity, expected pain intensity, and state negative affectivity. Trait negative affectivity and uncontrollability showed no significant effect, presumably because of the low number of included studies. Thus, further investigation is necessary to clearly determine their role in unpredictable pain perception.