The journal of pain : official journal of the American Pain Society
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This study investigated the effects of a threatening and a safe social context on learning pain-related fear, a key factor in the development and maintenance of chronic pain. We measured self-reported pain intensity, pain expectancy, pain-related fear (verbal ratings and eyeblink startle responses), and behavioral measures of avoidance (movement-onset latency and duration) using an established differential voluntary movement fear conditioning paradigm. Participants (N = 42) performed different movements with a joystick: during fear acquisition, movement in one direction (CS+) was followed by a painful stimulus (pain-US) whereas movement in another direction (CS-) was not. For participants in the threat group, an angry face was continuously presented in the background during the task, whereas in the safe group, a happy face was presented. During the extinction phase the pain-US was omitted. As compared to the safe social context, a threatening social context led to increased contextual fear and facilitated differentiation between CS+ and CS- movements regarding self-reported pain expectancy, fear of pain, eyeblink startle responses, and movement-onset latency. In contrast, self-reported pain intensity was not affected by social context. These data support the modulation of pain-related fear by social context. ⋯ A threatening social context leads to stronger acquisition of (pain-related) fear and simultaneous contextual fear but does not affect pain intensity ratings. This knowledge may aid in the prevention of chronic pain and anxiety disorders and shows that social context might modulate pain-related fear without immediately affecting pain intensity itself.
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Lumbopelvic pain is common in pregnancy but the sensitization factors underlying the condition are largely unknown. This study characterized the somatosensory profile of pregnant and nonpregnant women and the relationship between pain, hypersensitivity, and commonly used manual clinical tests. Thirty-nine pregnant and 22 nonpregnant women were included. Although lumbopelvic pain was not an inclusion criterion, the pregnant women were divided into low- and high-pain groups following data collection. The sensitivity to light brush, pin-prick, and pressure pain was assessed bilaterally at 3 sites in the lumbopelvic region, at the shoulder, and in the lower leg. Responses to the active straight leg raise test and pain provocation tests of the sacroiliac joint were recorded. Participants completed questionnaires addressing emotional and physical well-being and rated disability using the Pelvic Girdle Questionnaire. Compared with controls, the high-pain group rated the active straight leg raise test as more difficult (P < .05), and both pain groups had more positive pain provocation tests (P < .05). The pregnant groups demonstrated significantly lower pressure pain thresholds at most assessment sites compared with controls (P < .05), but self-reported disability and pain were not correlated with pressure pain thresholds within pregnant participants. The high-pain group reported worse emotional health and poorer sleep quality than controls (P < .05). ⋯ This article presents the somatosensory profile of a healthy pregnant cohort. The results indicate that pain sensitivity increases during pregnancy possibly owing to the physical changes the body undergoes during pregnancy but also owing to changes in emotional health. This should be accounted for in clinical management of pregnant women with lumbopelvic pain.
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The Pain Self-Efficacy Questionnaire (PSEQ) is an established 10-item measure of pain self-efficacy that is widely used in clinical and research settings. However, a shorter measure would reduce patient and researcher burden and save valuable time in busy clinical settings. The aim of this study was to develop and confirm the psychometric properties of a valid and reliable 2-item short form of the PSEQ (PSEQ-2). We used a large sample of 1,418 chronic pain patients, which we randomly split into 2 smaller groups. We identified the 2 short-form items in Sample 1 and confirmed their properties in Sample 2. In order to identify the 2 items for the short-form measure, we selected the first item based on the highest item-total correlation. The second item was identified after a series of additional analyses. The 2 items identified from the PSEQ reflected confidence in one's ability to work and lead a normal life despite pain. The PSEQ-2's validity and internal consistency were found to be sound. Test-retest reliability, sensitivity to change, and convergent validity were confirmed in a separate patient sample (n = 140) that had recently completed an intervention designed, in part, to modify self-efficacy beliefs. The PSEQ-2 appears to be a robust measure of pain self-efficacy. ⋯ Pain self-efficacy is a belief in one's ability to carry out activities even when in pain and is important in coping effectively with pain. A short measure of pain self-efficacy was developed and evaluated. It appears to be suitable for use in clinical and research settings.
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Randomized Controlled Trial
Effect of types and anatomic arrangement of painful stimuli on conditioned pain modulation.
Reduced pain perception during painful stimulation to another body region (ie, conditioned pain modulation [CPM]) is considered important for pain modulation and development of pain disorders. The various methods used to study CPM limit comparison of findings. We investigated the influence of key methodologic variations on CPM and the properties of CPM when the back is used for the test stimulus or the conditioning stimulus (CS). Two different test stimuli (pressure pain threshold and pain response to suprathreshold heat [Pain-45, ie, pain rated at 45 on a 0-100 numeric rating scale]) were assessed before and during application of a noxious or non-noxious (sham) CS. Eight blocks of trials varied the anatomic location (back and forearms) and arrangement (body side) of the stimuli. Pressure pain threshold (as the test stimulus) increased during application of noxious, but not non-noxious, CS when stimuli were applied to opposite body sides or heterotopic sites on one body side. Inconsistent with pain-induced CPM, Pain-45 decreased during both noxious and non-noxious CS. These findings indicate that 1) pressure pain threshold can be more confidently interpreted with respect to CPM evoked by a painful stimulus than Pain-45, 2) the back and forearm are equally effective as sites for stimuli, and 3) stimuli arrangement does not influence CPM, except for identical anatomic regions on the same body side. ⋯ This study indicates that pressure pain threshold as the test stimulus provides a more valid measure of pain-induced CPM than pain response to a suprathreshold heat stimulus. Induction and magnitude of CPM is independent of stimuli arrangement, as long as ipsilateral homotopic sites are avoided. These findings clarify methods to study CPM.
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Review Meta Analysis
Placebo responses in long-standing complex regional pain syndrome: a systematic review and meta-analysis.
The typical placebo response (ie, the nonspecific effects in the placebo group including benign natural course, regression to the mean, expectation/conditioning effects, and others) in randomized trials in complex regional pain syndrome (CRPS) is unknown. We recently observed a surprising near-absence of placebo response in a randomized controlled trial we conducted on patients with long-standing (≥6 months) CRPS. To investigate the idea that there may be an absence of placebo response in long-standing CRPS further, we conducted a systematic review and meta-analysis of placebo responses in randomized controlled trials conducted in patients with CRPS of ≥6 months. We systematically identified suitable randomized controlled trials published between 1966 and September 2013. We calculated the mean difference and standard error of the mean difference for placebo responses and synthesized individual effect sizes at 4 specified time periods of interest (15-30 minutes, 1 week, 3-4 weeks, and 6 weeks or more) via meta-analysis using the method of inverse-variance. Heterogeneity was assessed according to the I(2) statistic. For primary analysis, we pooled trial-specific effect sizes over the 4 time points. We analyzed data from 340 participants from 18 trials out of a possible 361 participants from 20 trials (94% of participants analyzed). Significant heterogeneity was present between trials; therefore, we interpreted trends from visual inspection of individual trials and pooled estimates. Placebo response was significant at the earliest time period (15-30 minutes). There was no significant evidence of placebo response at any of the other time periods. These results inform the design of future trials, and they caution against the "therapeutic" use of placebo in long-standing CRPS. ⋯ In this meta-analysis of placebo responses in randomized controlled trials in long-standing CRPS, published during 1966 to 2013, we found no evidence for placebo analgesia, except at very early time points. Results inform the design of future placebo analgesia research in long-standing CRPS.