Pain
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Comparative Study
Effects of mood on pain responses and pain tolerance: an experimental study in chronic back pain patients.
Although chronic pain and depression commonly co-occur, causal relationships have yet to be established. A reciprocal relationship, with depression increasing pain and vice versa, is most frequently suggested, but experimental evidence is needed to validate such a view. The most straightforward approach would be a demonstration that increasing or decreasing depressed mood predictably modifies pain responses. ⋯ Results indicate that the induction of depressed mood resulted in significantly higher pain ratings at rest and lower pain tolerance, whilst induced happy mood resulted in significantly lower pain ratings at rest and greater pain tolerance. Correlations between changes in mood on the one hand and changes in pain response and pain tolerance on the other hand were consistent with these findings. It is concluded that, in chronic back pain patients, experimentally induced negative mood increases self-reported pain and decreases tolerance for a pain-relevant task, with positive mood having the opposite effect.
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Comparative Study
Combined effects of major depression, pain and somatic disorders on general functioning in the general adult population.
This study was carried out to assess the prevalence of major depressive disorder (MDD) in persons suffering from pain symptoms in various locations, both with and without comorbid somatic disorders and to analyze the single and combined effects of MDD, pain symptoms and somatic disorders on general functioning in the community. The 12-month prevalence of MDD, somatic disorders and pain symptoms, grouped according to location, were determined among 4181 participants from a community sample. Depression was assessed utilising the Composite International Diagnostic Interview. ⋯ The presence of pain increases risk of associated MDD. The number of pain locations experienced, rather than the specific location of pain, has the greatest impact on general functioning. Not only chronic pain, but pain of any type may be an indicator of MDD and decreased general functioning.
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Comparative Study
Sensitization of primary afferents to mechanical and heat stimuli after incision in a novel in vitro mouse glabrous skin-nerve preparation.
In this study, we recorded activity from afferent fibers innervating the mouse plantar skin, the same region evaluated in pain behavior experiments. We compared responses of afferents from incised and unincised hind paw skin. The plantar skin together with attached medial and lateral plantar nerves was dissected until they could be completely removed intact and placed in an organ bath chamber continuously perfused with oxygenated Kreb's solution with the temperature maintained at 32 degrees C. ⋯ Few fibers were excited by cooling. Heat sensitization of primary afferents was more prominent when activities of unclassified afferents are included. The preparation allows us to study afferent function of the same tissue that is examined for in vivo pain behavior assays in mice.
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Randomized Controlled Trial Multicenter Study Comparative Study
Gabapentin in traumatic nerve injury pain: a randomized, double-blind, placebo-controlled, cross-over, multi-center study.
A double-blind, randomized, placebo-controlled cross-over multi-center study was conducted to evaluate the efficacy and safety of gabapentin in the treatment of neuropathic pain caused by traumatic or postsurgical peripheral nerve injury, using doses up to 2400 mg/day. The study comprised a run-in period of two weeks, two treatment periods of five weeks separated by a three weeks' washout period. The primary efficacy variable was the change in the mean pain intensity score from baseline to the last week of treatment. ⋯ Both the Patient (p=0.023) and Clinician (p=0.037) Global Impression of Change indicated a better response with gabapentin compared with placebo. Gabapentin was well tolerated. The most common adverse effects were dizziness and tiredness.
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Comparative Study
Principle components analysis of pain thresholds to thermal, electrical, and mechanical stimuli suggests a predominant common source of variance.
We addressed the question whether pain thresholds to different stimuli measure independent aspects of pain or one common phenomenon. In the first case, different stimuli are required to completely characterize a subject's pain sensitivity. In the second case, different stimuli are redundant and can be used to calculate composite scores across pain modalities. ⋯ Only minor variance components, each explaining <14% of the total variance, indicated a distinction of pain stimuli. There, a pattern of similarities and dissimilarities emerged agreeing with known distinct mechanisms of nociceptive responses to different stimuli. We conclude that characterizing a person as being generally stoical or complaining to any painful stimulus appears to be justified at least at pain threshold level.