The journal of pain : official journal of the American Pain Society
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Review Meta Analysis
Is pain perception altered in people with depression? A systematic review and meta-analysis of experimental pain research.
Although clinical studies suggest depressed patients may be more vulnerable to pain, experimental research is equivocal. This meta-analysis aimed to clarify whether depression is associated with altered pain perception in response to noxious stimulation and to identify factors that might influence this association. A search of major electronic databases was conducted to identify experimental studies investigating pain response in depressed participants versus healthy control participants using established pain outcome measures. ⋯ However, considerable heterogeneity in the direction and magnitude of effects was observed, indicating a likely condition-specific effect of depression on pain. Subgroup analysis found that pain threshold/tolerance was increased in depression for exteroceptive (cutaneous) stimulation but decreased for interoceptive (ischemic) stimulation, but that substantial heterogeneity remained. Overall, results provide some support for altered pain processing in depression, but suggest this link is dependent upon modality and additional, unidentified factors.
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Somatic awareness (SA) refers to heightened sensitivity to a variety of physical sensations and symptoms. Few attempts have been made to dissociate the relationship of SA and affective symptoms with pain outcomes. We used a validated measure of mood and anxiety symptoms that includes questions related to SA to predict the number of tender points found on physical examination in a large cross-sectional community sample (the Midlife in the United States [MIDUS] Biomarker study). ⋯ Follow-up mediation analyses indicated that the relationship between general distress and tender points was partially mediated by levels of SA. Our primary finding was that SA is strongly related to the number of tender points in a community sample. Mechanisms linking SA to the spatial distribution of pain sensitivity should be investigated further.
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Evidence suggests that pain patients who report lifetime abuse experience greater psychological distress, have more severe pain and other physical symptoms, and greater functional disability. The aim of the present study was to determine the associations between a history of lifetime abuse and affective distress, fibromyalgianess (measured using the 2011 Fibromyalgia Survey), pain severity and interference, and physical functioning. A cross-sectional analysis of 3,081 individuals presenting with chronic pain was performed using validated measures and a history of abuse was assessed via patient self-report. ⋯ Mediation models showed that the Fibromyalgia Survey score and affective distress independently mediate the relationship between abuse and pain severity and physical functioning (Ps < .001). Our mediation models support a novel biopsychosocial paradigm wherein affective distress and fibromyalgianess interact to play significant roles in the association between abuse and pain. We posit that having a centralized pain phenotype underlies the mediation of increased pain morbidity in individuals with a history of abuse.
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Dorsal root ganglion (DRG) electrical stimulation (ganglionic field stimulation [GFS]) is effective in relieving clinical pain, but its mechanism is unknown. We therefore developed a rat model for GFS to test analgesic effects in the context of neuropathic pain. GFS was applied with a bipolar electrode at L4, using parameters replicating clinical use (20 Hz, 150-μs pulse width, current at 80% of motor threshold). ⋯ Conditioned place preference showed that GFS was not rewarding in uninjured control animals but was rewarding in animals subjected to TNI, which reveals analgesic efficacy of GFS for spontaneous pain. We conclude that GFS relieves neuropathic pain in rats. This model may provide a platform for identifying mechanisms and novel applications of GFS.