Human Studies

Non-specific chronic low back pain (CLBP) is a multifactorial disorder. Pain-related fear and altered movement preparation are considered to be key factors in the chronification process. Interactions between both have been hypothesized, but studies examining the influence of situational fear on movement preparation in low back pain (LBP) are wanting, as well as studies differentiating between recurrent LBP (RLBP) and CLBP. Therefore, this study examined whether experimentally induced pain-related fear influences movement preparation. In healthy controls (n=32), RLBP (n=31) and CLBP (n=30) patients central and peripheral measures of movement preparation were assessed by concurrently measuring trunk muscle anticipatory postural adjustments (APA) with EMG and Contingent Negative Variation (CNV) with EEG during performance of rapid arm movements (RAM). Two conditions were compared, one without (no fear) and one with (fear) possibility of painful stimulation to the back during RAM. Visual analogue scales were used to assess pain-related expectations/fear in both conditions. The experimentally induced fear of pain during movement performance led to an increase in CNV-amplitude, which was similar in all three groups. Concerning APAs no effects of fear were found, but group differences with generally delayed APAs in CLBP compared to controls and RLBP patients were evident. These results suggest that with fear an attentional redirection towards more conscious central movement preparation strategies occurs. Furthermore, differences in movement preparation in RLBP and CLBP patients exist, which could explain why RLBP patients have more recovery capabilities than CLBP.

Recent research has shown that placebos can be effective even if they are openly prescribed to participants. Yet, it is unclear how such "open-label placebos" (OLPs) compare to deceptive placebo (DP) and what the mechanisms of actions are. In this study, we therefore compared 2 versions of OLP to DP and no treatment (NT).

Pain, fatigue, and depression commonly co-occur as a symptom cluster in pathological inflammatory states. Psychosocial stressors such as loneliness may lead to similar states through shared mechanisms. We investigated the association of loneliness with pain, fatigue, and depression in older adults. Using Health and Retirement Study data ( = 11,766), we measured cross-sectional prevalence of frequent, moderate to severe pain; severe fatigue; depressive symptoms; and co-occurrence of symptoms surpassing threshold levels (i.e., symptom cluster). Logistic regression models evaluated associations with loneliness. Pain, fatigue, and depression were reported in 19.2%, 20.0%, and 15.3% of the total sample, respectively. The symptom cluster was seen in 4.9% overall; prevalence in lonely individuals was significantly increased (11.6% vs. 2.3%,  < .0001). After adjusting for demographic variables, loneliness associated with the symptom cluster (adjusted OR = 3.39, 95% CI = 2.91, 3.95) and each symptom (pain adjusted OR = 1.61, 95% CI = 1.48, 1.76; fatigue adjusted OR = 2.02, 95% CI = 1.85, 2.20; depression adjusted OR = 4.34, 95% CI = 3.93, 4.79). Loneliness strongly associates with the symptom cluster of pain, fatigue, and depression. Further research should examine causal relationships and investigate whether interventions targeting loneliness mitigate pain, fatigue, and depression.

To compare somatosensory function profiles and psychologic factors in patients with primary burning mouth syndrome (BMS) and healthy controls and to evaluate correlations of subjective pain ratings with somatosensory and psychologic parameters.

This study aims to (1) examine the temporal influence of peer victimization on mood, sleep quality, pain, and activity limitations in clinical and community samples of youth, and (2) test mood and sleep as mediators of peer victimization-pain pathways. One hundred fifty-six adolescents (n=74 chronic pain group) completed a week of online diary monitoring assessing their daily peer victimization experiences, negative mood, sleep quality, pain intensity, and pain-related activity limitations. In multilevel models controlling for group status, person-mean peer victimization (averaged across days) significantly predicted worse mood, pain, and activity limitations (all ps < .01) while daily victimization predicted worse mood (p < .05). Results from within-person mediation indicated a significant indirect effect of daily peer victimization on next-day activity limitations, through daily negative mood. Results from between-person mediation indicated that negative mood significantly mediated the relation between peer victimization and pain and the relation between peer victimization and activity limitations. Peer victimization is associated with negative health indicators in clinical and community samples of youth and may exert its influence on pain and pain-related activity limitations through negative mood. PERSPECTIVE: This article examines the temporal influence of peer victimization on pain in adolescents with and without chronic pain, and examines mood and sleep quality as mechanisms linking victimization to pain. This information may be useful for pain prevention researchers as well as providers who assess and treat pain in childhood.

Fibromyalgia is a syndrome characterized by chronic widespread pain, with a multifactorial etiopathogenesis and high incidence of neuropsychiatric comorbidity. It has been inaccurately considered a pathological condition affecting only middle-aged women. The study aimed to explore the association of sociodemographic and clinical factors in patients with fibromyalgia with depression and/or anxiety. The present study is an analysis of a cross-sectional study of a secondary source. The prevalence ratio (PR) between the demographic and clinical variables of patients with fibromyalgia and concomitant depression and/or anxiety was calculated. Overall, 1,106 medical records were obtained with a confirmed diagnosis of fibromyalgia between 2010 and 2016; of these, 318 (28.75%) patients had an associated diagnosis of depression and/or anxiety. Approximately 28% women (295 of 1,052) and 42.6% men (23 of 54) suffered from depression and/or anxiety. In the adjusted explanatory model of depression and/or anxiety in patients with fibromyalgia, the relationship between sex (female PR = 0.5 [0.28-0.86]) and low socioeconomic strata (PR = 0.53 [0.33-0.70]) remained constant. In the study population, patients with fibromyalgia belonging to lower social strata were less likely to present with depression and anxiety. The male sex may pose as a risk factor for depression and/or anxiety in patients with fibromyalgia. Fibromyalgia has a huge impact on men's physical as well as mental health.

We explored the ongoing question of whether placebo analgesia alters afferent nociceptive processing in a novel paradigm designed to minimize the role of response bias in placebo measurement. First, healthy adult participants received a standard heat placebo induction and conditioning procedure using a topical "analgesic" cream applied to one arm. During a subsequent placebo testing procedure, participants rated stimuli on the placebo-treated arm and untreated arm, using a task that minimized subjects' ability to guess the expected response, thus reducing experimenter demand. Retrospectively participants reported moderate analgesia effectiveness (mean=5.3/10), but for individual temperature ratings, only 2 subjects exhibited a perceptual placebo response >5 points. Next, these subjects completed a novel, exploratory task designed to measure changes in inter-arm in discriminative accuracy that would be expected from changes in afferent nociception. Both placebo responders (but no non-responders) showed reduced discriminative ability when the hotter stimulus occurred on the placebo arm, an effect consistent with alterations in nociceptive afferent flow and unlikely to be caused by response bias.

Non-restorative sleep is a key diagnostic feature of the musculoskeletal pain disorder fibromyalgia, and is robustly associated with poor physical functioning, including activity interference. However, the mechanisms through which non-restorative sleep elicits activity interference among individuals with fibromyalgia at the within-person level remain unclear. The present study tested the following three-path mediation model, using data gathered from a 21-day electronic daily diary in 220 individuals with fibromyalgia: previous night non-restorative sleep → morning pain catastrophizing → afternoon pain severity → end-of-day activity interference. Results of multilevel structural equation modeling supported the three-path mediation model. Previous night's non-restorative sleep and morning pain catastrophizing were also directly related to end-of-day activity interference. Previous night non-restorative sleep did not significantly predict afternoon pain severity while controlling for the effect of morning pain catastrophizing. Greater non-restorative sleep during the previous night and a higher level of morning pain catastrophizing appear to serve as risk factors for experiencing greater daily pain and activity interference later in the day. These findings point to the potential utility of targeted interventions that improve both sleep quality and pain catastrophizing to help individuals with chronic pain engage in important daily activities despite experiencing pain.