Pain
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We described trends in pelvic pain characteristics over 2 years of follow-up among adolescents and adults with and without endometriosis participating in the longitudinal observational cohort of the Women's Health Study: From Adolescence to Adulthood, using data reported at baseline and at years 1 and 2 of follow-up. Participants completed a questionnaire at baseline (between November 2012 and May 2019) and annually thereafter that included validated measures of severity, frequency, and life interference of dysmenorrhea, acyclic pelvic pain, and dyspareunia. Our study population included 620 participants with surgically confirmed endometriosis (rASRM stage I/II = 95%) and 671 community-based and hospital-based controls, with median age = 19 and 24 years, respectively. ⋯ Trends among controls remained fairly stable across 2 years. Among endometriosis cases who completed the questionnaire at all 3 time points, 18% reported persistent, severe acyclic pelvic pain at all 3 time points. Over time, different trends were observed by pelvic pain type among endometriosis cases and controls, supporting the importance of assessing multidimensional features of pelvic pain.
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Nociceptive information from the orofacial area projects to the trigeminal spinal subnucleus caudalis (Sp5C) and is then conveyed to several nuclei, including the parabrachial nucleus (PBN). The insular cortex (IC) receives orofacial nociceptive information and sends corticofugal projections to the Sp5C. The Sp5C consists of glutamatergic and GABAergic/glycinergic interneurons that induce excitatory postsynaptic currents and inhibitory postsynaptic currents, respectively, in projection neurons. ⋯ Moreover, selective stimulation of IC axons increased the firing rate at the threshold responses. Finally, we demonstrated that selective stimulation of IC axons in the Sp5C by a chemogenetic approach decreased the thresholds of both mechanical and thermal nociception. Thus, IC projection to the Sp5C is likely to facilitate rather than suppress excitatory outputs from the Sp5C.
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Sham interventions in randomized clinical trials (RCTs) of physical, psychological, and self-management (PPS) therapies for pain are highly variable in design and believed to contribute to poor internal validity. However, it has not been formally tested whether the extent to which sham controls resemble the treatment under investigation consistently affects trial outcomes, such as effect sizes, differential attrition, participant expectancy, and blinding effectiveness. Placebo- or sham-controlled RCTs of PPS interventions of clinical pain populations were searched in 12 databases. ⋯ The results support the supposed link between blinding methods and effect sizes, based on a large and systematically sourced overview of methods. However, challenges to effective blinding are complex and often difficult to discern from trial reports. Nonetheless, these insights have the potential to change trial design, conduct, and reporting and will inform guideline development.
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Meta Analysis
The association between personality traits and placebo effects: a preregistered systematic review and meta-analysis.
Placebo effects are ubiquitous yet highly variable between individuals and therefore strongly affect clinical trial outcomes such as pain relief. It is unclear whether dispositional psychological traits influence responsiveness to placebo. This preregistered meta-analysis and systematic review synthesized the literature investigating the association between personality traits and placebo effects. ⋯ We did not find evidence of associations between any of these traits and magnitude of placebo effects, which was supported by equivalence tests. Furthermore, we did not find evidence for moderating factors such as placebo manipulation type (conditioning or nonconditioning) or condition (pain or nonpain). These findings challenge the notion that personality influences responsiveness to placebos and contradict its utility for identifying placebo "responders" and "nonresponders."