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Background and aims The placebo response has been identified as one factor responsible for the lack of therapeutic trials with positive outcomes in neuropathic pain. Reviews have suggested that certain neuropathic pain conditions, including HIV-associated sensory neuropathy (HIV-SN), exhibit a greater placebo response than other neuropathic aetiologies. If true, such a finding could substantially affect clinical trial design and therapeutic developments for these conditions. This study aimed to identify any difference in placebo response between trials of systemic pharmacological intervention in HIV-SN and a comparable neuropathic condition, diabetic polyneuropathy (DPN) and to identify factors influencing the placebo response. Methods A systematic review search to identify randomised, double-blind studies of systemic pharmacological interventions for painful HIV-SN and DPN published between January 1966 and June 2019 was performed. A meta-analysis of the magnitude of placebo response and the proportion of placebo responders was conducted and compared between the two disease conditions. A meta-regression was used to assess for any study and participant characteristics that were associated with the placebo response. Only studies meeting a methodological quality threshold were included. Results Seventy-five trials were identified. There was no statistically significant difference in the proportion of placebo responders (HIV-SN = 0.35; versus DPN = 0.27, p = 0.129). The difference observed in the magnitude of the placebo response [pain reduction of 1.68 (1.47-1.88) DPN; 2.38 (1.87-2.98) in HIV-SN] was based on only 2 trials of HIV-SN and 35 of DPN. Potential factors influencing the placebo response such as psychological measures, were reported inconsistently. Conclusions We found no statistically significant difference in the placebo response rate between painful HIV-SN and DPN. Too few studies were available that reported the necessary information to clarify potential differences in the magnitude of placebo response or to elucidate parameters that could be contributing such differences. Implications The placebo response is one factor that may contribute to a lack of positive trials in neuropathic pain; some etiologies may display larger responses than others. This meta-analysis found no significant difference in placebo response between trials of HIV-associated sensory neuropathy and painful diabetic polyneuropathy, although limited data were available.
Learn More >Low back pain (LBP) is a highly prevalent and disabling condition whose initiating factors are poorly understood. It is known that psychological and physical stress is associated with LBP but the causal relationship, mechanisms and mediators have not been elucidated, and a preclinical model enabling the investigation of causality and thereby critically contributing to clinical translation does not exist.In the present study, we first established and characterized a myofascial LBP model in mice based on NGF injection into the low back muscles. Secondly, we investigated the effect of two different stress paradigms on this mouse LBP model by applying the chronic unpredictable stress (CUS) and vertical chronic restraint stress (vCRS) paradigms, to mimic psychological and psychophysical stress, respectively. In these studies, we combined longitudinal behavioral tests with gene and protein expression analysis in the muscle, dorsal root ganglia and spinal cord. NGF-induced LBP was characterized by long-lasting local and plantar mechanical hypersensitivity, cold hyperalgesia, decreased grip strength and wheel running activity, and time-dependent changes of neuropeptide and glial markers in the spinal cord. Interestingly, the exposure to CUS slightly worsened pain behavior, whereas vCRS primed and highly aggravated pain in this LBP model, by causing per se the intramuscular upregulation of endogenous NGF and increased spinal astrocyte expression.Our mouse model, particularly the combination of NGF injection and vCRS suggest that similar mechanisms are important in non-specific LBP and might help to investigate certain aspects of stress-induced exacerbation of pain.
Learn More >Background and aims Previous research on pain and cognition has largely focused on non-social cognitive outcomes (e.g. attention, problem solving). This study examines the relationship between pain and stereotyping, which constitutes a fundamental dimension of social cognition. Drawing on dual process theories of cognition, it was hypothesized that higher levels of pain would increase stereotyped judgments based on ethnicity and age. The hypothesis was tested in conjunction with experimentally induced pain (Study 1) and clinical pain (Study 2). Methods In Study 1, experimental pain was induced with the cold pressor method on a between-subjects basis. Participants (n = 151) completed a judgment task that assessed to what extent they relied on stereotypes (ethnic and age) when estimating other people's cognitive performance. In Study 2, 109 participants with clinical, musculoskeletal pain completed the same stereotype judgment task. Correlations between stereotyped judgments and various pain qualities (intensity, interference with daily activities, duration, and persistence) were performed. Results In Study 1, pain induced participants did not form significantly more stereotyped judgments compared to pain-free participants. However, higher reported pain intensity was associated with more ethnically stereotyped judgments. In Study 2, there were no significant correlations between different aspects of clinical pain and stereotyped judgments. Conclusions The results provide weak support for the hypothesis that pain increases stereotyped judgments. This was the case for both experimentally induced pain and clinical pain. The present study is the first to investigate the link between pain and stereotyping, suggesting that stereotypical judgments may be a social cognitive outcome that is relatively unaffected by pain. Implications The results have practical implications for the clinic, for example, where chronic pain patients may not have greater difficulties interacting with health care professionals that are members of a stereotyped social group (e.g. ethnic).
Learn More >The aims of this study were twofold: 1) to better understand the associations between pain-related cognitions and pain severity, and psychological and physical function, and 2) to determine the extent to which these cognitions function as mediators in the association between pain severity and depression in a sample of primary care adult patients with chronic pain and depression.
Learn More >Biopsychosocial integrated pain team (IPT) care models are being implemented in Veterans Health Administration (VA) and other health care systems to address chronic pain and reduce risks related to long-term opioid therapy, with little evaluation of effectiveness to date. We examined whether IPT improves self-reported pain-related outcomes and opioid misuse.
Learn More >Mindfulness-based interventions have been receiving growing attention in cancer care.
Learn More >Chronic pain and opioid use are associated with increased risk for suicidal ideation and behaviors (SIB) in cross-sectional studies, particularly among individuals who catastrophize about their pain. This study examined the longitudinal association between two styles of pain coping, catastrophizing and hoping/praying, as predictors of subsequent SIB, as well as possible mediators of this association among patients with chronic pain receiving long-term opioid therapy. Participants (n = 496) were adults with chronic nonmalignant pain on long-term opioid therapy who did not develop an opioid use disorder. Participants were assessed for pain coping, suicidal ideation, depression, social support and pain interference at baseline, and were reassessed for SI, depression, and pain interference at 6- and 12-month follow-ups. Catastrophizing was a significant predictor of increased subsequent SIB, whereas hoping/praying did not protect against future SIB. The relationship between catastrophizing and future SIB was mediated by depression, but not social support or pain interference. In conclusion, catastrophizing was an important predictor of subsequent SIB due to its effect on increasing depression among patients with chronic nonmalignant pain receiving long-term opioid therapy. Future research should explore the extent to which targeting catastrophizing reduces subsequent depression and suicide risk.
Learn More >Chronic musculoskeletal pain is a complex medical condition that can significantly impact quality of life. Patients with chronic pain demonstrate attentional biases towards pain-related information. The therapeutic benefits of modifying attentional biases by implicitly training attention away from pain-related information towards neutral information have been supported in a small number of published studies. Limited research however has explored the efficacy of modifying pain-related biases via the internet. This protocol describes a randomised, double-blind, internet-delivered attentional bias modification intervention, aimed to evaluate the efficacy of the intervention on reducing pain interference. Secondary outcomes are pain intensity, state and trait anxiety, depression, pain-related fear, and sleep impairment. This study will also explore the effects of training intensity on these outcomes, along with participants' perceptions about the therapy.
Learn More >Conditioned pain modulation (CPM) and manipulation induced analgesia (MIA) are two forms of endogenous analgesia. Many forms of analgesia can be influenced by the nature of the patient clinician interaction. The aim of this study was to evaluate the influence of an empathetic and supportive interaction on CPM and MIA in people with Lateral Epicondylalgia (LE).
Learn More >Pediatric chronic pain has often been examined from a risk perspective, and relatively less is known about the individual and family-level resilience factors that help youth with chronic pain maintain their quality of life. This cross-sectional study: (a) examined the relations among purported youth and parent resilience (youth pain acceptance and pain self-efficacy, parent psychological flexibility) and risk (youth pain intensity, parent protectiveness) factors with youth quality of life, and (b) tested exploratory statistical mechanisms that may explain relations between parent and youth variables.
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