Robert R. Edwards

Pain catastrophizing: a critical review

Pain catastrophizing is conceptualized as a negative cognitive–affective response to anticipated or actual pain and has been associated with a number of important pain-related outcomes. In the present review, we first focus our efforts on the conceptualization of pain catastrophizing, highlighting its conceptual history and potential problem areas. We then focus our discussion on a number of theoretical mechanisms of action: appraisal theory, attention bias/information processing, communal coping, CNS pain processing mechanisms, psychophysiological pathways and neural pathways. We then offer evidence to suggest that pain catastrophizing represents an important process factor in pain treatment. We conclude by offering what we believe represents an integrated heuristic model for use by researchers over the next 5 years; a model we believe will advance the field most expediently.

Ethnic Differences in Pain Tolerance: Clinical Implications in a Chronic Pain Population

Objective Although numerous studies have independently examined ethnic differences in clinical and experimental pain, few have investigated differences in both sensitivity to controlled noxious stimuli and clinical pain reports in the same sample. The present experiment examined the effects of ethnicity (African American vs. white) on experimental pain tolerance and adjustment to chronic pain. Methods Three hundred thirty-seven (68 African American and 269 white) patients with chronic pain referred to a multidisciplinary treatment center participated in the study. In addition to completing a number of standardized questionnaires assessing adjustment to chronic pain, participants underwent a submaximal effort tourniquet procedure. This experimental pain procedure yields a measure of tolerance for a controlled noxious stimulus (ie, arm ischemia). Results African American subjects reported higher levels of clinical pain as well as greater pain-related disability than white participants. In addition, substantial group differences were observed for ischemic pain tolerance, with African Americans demonstrating less tolerance than whites. Correlational analyses revealed a small but significant inverse relationship between ischemic pain tolerance and the reported severity of chronic pain. Conclusions Collectively these findings support previous research revealing ethnic differences in responses to both clinical and experimental pain. Moreover, the present results suggest that enhanced sensitivity to noxious stimuli on the part of African Americans may be associated with ethnic differences in reported clinical pain, although the magnitude of ethnic differences was much greater for ischemic pain tolerance than for clinical pain measures.

Recommendations on terminology and practice of psychophysical DNIC testing

a Department of Neurology, Rambam Health Care Campus, Technion Faculty of Medicine, Haifa, Israel b Department of Diagnostic Sciences, UMDNJ, Newark, NJ, USA c Laboratory of Experimental Pain Research, Aalborg University, Aalborg, Denmark d Hopital Ambroise Pare, Boulogne Billancourt, France e Department of Anesthesiology, Brigham and Women’s Hospital, Harvard Medical School Boston, MA, USA f College of Dentistry, University of Florida, Gainesville, FL, USA g Faculty of Health and Welfare Studies, University of Haifa, Haifa, Israel h Department of Molecular Medicine and Surgery, Karolinska Hospital/Institutet, Stockholm, Sweden i Department of Psychology, Bamberg University, Bamberg, Germany j Department of Surgery and Neurosurgery, Faculty of Medicine, Sherbrooke University, Sherbrooke, QC, Canada k Department of Anesthesiology, Radboud University, Nijmegen, Netherlands

Age-related differences in endogenous pain modulation: a comparison of diffuse noxious inhibitory controls in healthy older and younger adults

&NA; Despite decades of research, hundreds of studies, and a number of recent reviews, the effects of aging on the experience of pain remain poorly understood. Many prior investigators have reported increases in persistent pain conditions and diminished tolerance for certain types of laboratory‐induced pain among the elderly. While explanations for these effects often propose senescent decrements in endogenous analgesic systems as a possible contributory mechanism, almost no direct empirical evidence for this hypothesis has yet emerged in human studies. The present investigation was designed to evaluate the existence and nature of these putative age‐related differences in endogenous pain inhibition. Groups of healthy younger (n=45, mean age=21.6 years, range=18–25) and older (n=48, mean age=63.1 years, range=55–67) adults participated in a controlled, two‐session laboratory assessment of diffuse noxious inhibitory controls (DNIC), a measure of endogenous pain inhibition. In this study, we examined age differences in the effects of concurrent cold pain on ratings of heterotopically presented repetitive noxious thermal stimuli. Interestingly, older adults demonstrated facilitation rather than inhibition of thermal pain during concurrent noxious cold stimulation while younger adults demonstrated some expected DNIC effects (i.e. a reduction in thermal pain ratings during heterotopic stimulation with noxious cold). Collectively, the findings of the present study suggest age‐associated decrements in at least one form of endogenous analgesic response. If replicated, such findings of reduced pain‐modulatory capacity in the elderly may partially explain age‐related differences in the prevalence, severity, and impact of chronic pain.

ETHNIC DIFFERENCES IN RESPONSES TO MULTIPLE EXPERIMENTAL PAIN STIMULI

&NA; A growing body of literature suggests that the experience of clinical pain differs across ethnocultural groups. Additionally, some evidence indicates greater sensitivity to experimentally induced pain among African Americans; however, most studies have included only one pain modality. This study examined ethnic differences in responses to multiple experimental pain stimuli, including heat pain, cold pressor pain, and ischemic pain. Heat pain threshold and tolerance, ratings of repetitive suprathreshold heat, and ischemic and cold pressor pain threshold and tolerance were assessed in 120 (62 African American, 58 white) healthy young adults. Also, several psychological instruments were administered. No ethnic group differences emerged for threshold measures, but African Americans had lower tolerances for heat pain, cold pressor pain and ischemic pain compared to whites. Ratings of intensity and unpleasantness for suprathreshold heat stimuli were significantly higher among African Americans. African Americans reported greater use of passive pain coping strategies and higher levels of hypervigilance. Controlling for passive pain coping did not account for group differences in pain responses, while controlling for hypervigilance rendered group differences in heat pain tolerance and ischemic pain tolerance non‐significant. These findings demonstrate differences in laboratory pain responses between African Americans and whites across multiple stimulus modalities, and effect sizes for these differences in pain tolerance were moderate to large for suprathreshold measures. Hypervigilance partly accounted for group differences. Additional research to determine the mechanisms underlying these effects is warranted.

Individual differences in endogenous pain modulation as a risk factor for chronic pain

This review summarizes evidence, primarily from recent human studies, indirectly supporting a novel hypothesis: that the assessment of healthy individuals’ responses to standardized noxious stimuli in a controlled laboratory environment has important implications for the later risk of developing a broad spectrum of chronically painful conditions. Descriptions of many chronic pain syndromes note that the disorder (e.g., fibromyalgia, headache, complex regional pain syndrome) is associated with hypersensitivity to pain and with reduced endogenous inhibition of pain, implying that an individual’s processing of pain-related information changes with the onset of the syndrome. However, pain sensitivity and pain-inhibitory capacity are normally distributed along a wide continuum in the general population, and recent evidence suggests that heightened baseline pain sensitivity and reduced basal pain-inhibitory processing place individuals at greater risk for experiencing severe, acute, clinical pain (e.g., postoperative pain). More controversial is the hypothesis that such individual-difference characteristics confer risk for, or protection against, chronic pain; although only a single prospective study has been published, substantial indirect evidence supports the contention that greater basal pain sensitivity and reduced pain-inhibitory capacity may act as a diathesis for chronic pain. Long-term cohort studies are necessary to test this hypothesis; such research could yield insight into the nature of chronic pain and permit greater precision in selecting high-risk individuals for chronic pain prevention research.

Ethnic differences in thermal pain responses

OBJECTIVE Although numerous studies have reported ethnic differences in the prevalence and severity of clinical pain, little is known about how these differences affect the perception of experimental pain. The present experiment examined the effects of ethnicity (African American vs. white) on thermal pain responses in a healthy undergraduate population. METHODS Thirty white subjects (16 women and 14 men) and 18 African Americans (10 women and 8 men) participated in the study. Thermal testing included evaluation of the following: warmth thresholds, thermal pain thresholds, thermal pain tolerances, and magnitude estimates of both the intensity and unpleasantness of thermal pain (at 46 degrees, 47 degrees, 48 degrees, and 49 degrees C). RESULTS Although no group differences emerged for warmth thresholds, thermal pain thresholds, or pain intensity ratings, African Americans demonstrated lower thermal pain tolerances than whites. In addition, African Americans had smaller slopes and larger intercepts than whites for ratings of pain unpleasantness. Additional analyses suggested that these findings were a consequence of group differences in thermal pain unpleasantness ratings at the lowest temperatures assessed (46 degrees and 47 degrees C); at these temperatures, African Americans rated the stimuli as more unpleasant than whites. Finally, group differences in thermal pain tolerance and thermal pain unpleasantness ratings seemed to partially account for greater self-reported daily pain symptoms among African Americans. CONCLUSIONS Collectively, these findings seem to suggest ethnic differences in the perception of the affective-motivational dimension of thermal pain.

Value of quantitative sensory testing in neurological and pain disorders: NeuPSIG consensus

Summary Standards for conducting quantitative sensory testing (QST), which is a psychophysical method used to quantify somatosensory function in response to controlled stimuli in healthy subjects and patients, is discussed, and recommendations on the basis of current status of QST are presented. ABSTRACT Quantitative sensory testing (QST) is a psychophysical method used to quantify somatosensory function in response to controlled stimuli in healthy subjects and patients. Although QST shares similarities with the quantitative assessment of hearing or vision, which is extensively used in clinical practice and research, it has not gained a large acceptance among clinicians for many reasons, and in significant part because of the lack of information about standards for performing QST, its potential utility, and interpretation of results. A consensus meeting was convened by the Neuropathic Pain Special Interest Group of the International Association for the Study of Pain (NeuPSIG) to formulate recommendations for conducting QST in clinical practice and research. Research studies have confirmed the utility of QST for the assessment and monitoring of somatosensory deficits, particularly in diabetic and small fiber neuropathies; the assessment of evoked pains (mechanical and thermal allodynia or hyperalgesia); and the diagnosis of sensory neuropathies. Promising applications include the assessment of evoked pains in large‐scale clinical trials and the study of conditioned pain modulation. In clinical practice, we recommend the use QST for screening for small and large fiber neuropathies; monitoring of somatosensory deficits; and monitoring of evoked pains, allodynia, and hyperalgesia. QST is not recommended as a stand‐alone test for the diagnosis of neuropathic pain. For the conduct of QST in healthy subjects and in patients, we recommend use of predefined standardized stimuli and instructions, validated algorithms of testing, and reference values corrected for anatomical site, age, and gender. Interpretation of results should always take into account the clinical context, and patients with language and cognitive difficulties, anxiety, or litigation should not be considered eligible for QST. When appropriate standards, as discussed here, are applied, QST can provide important and unique information about the functional status of somatosensory system, which would be complementary to already existing clinical methods.

Pretreatment Psychosocial Variables as Predictors of Outcomes Following Lumbar Surgery and Spinal Cord Stimulation: A Systematic Review and Literature Synthesis

BACKGROUND In the multimodal treatment approach to chronic back pain, interventional back procedures are often reserved for those who do not improve after more conservative management. Psychological screening prior to lumbar surgery or spinal cord stimulation (SCS) has been widely recommended to help identify suitable candidates and to predict possible complications or poor outcome from treatment. However, it remains unclear which, if any, variables are most predictive of pain-related treatment outcomes. OBJECTIVE The intent of this article is to perform a systematic review to examine the relationship between presurgical predictor variables and treatment outcomes, to review the existing evidence for the benefit of psychological screening prior to lumbar surgery or SCS, and to make treatment recommendations for the use of psychological screening. RESULTS Out of 753 study titles, 25 studies were identified, of which none were randomized controlled trials and only four SCS studies met inclusion criteria. The methodological quality of the studies varied and some important shortcomings were identified. A positive relationship was found between one or more psychological factors and poor treatment outcome in 92.0% of the studies reviewed. In particular, presurgical somatization, depression, anxiety, and poor coping were most useful in helping to predict poor response (i.e., less treatment-related benefit) to lumbar surgery and SCS. Older age and longer pain duration were also predictive of poorer outcome in some studies, while pretreatment physical findings, activity interference, and presurgical pain intensity were minimally predictive. CONCLUSIONS At present, while there is insufficient empirical evidence that psychological screening before surgery or device implantation helps to improve treatment outcomes, the current literature suggests that psychological factors such as somatization, depression, anxiety, and poor coping, are important predictors of poor outcome. More research is needed to show if early identification and treatment of these factors through psychological screening will enhance treatment outcome.

Catastrophizing as a mediator of sex differences in pain: differential effects for daily pain versus laboratory-induced pain

Abstract Sex differences in the experience of pain have been widely reported, with females generally reporting more frequent clinical pain and demonstrating greater pain sensitivity. However, the mechanisms underpinning such differences, while subject to intense speculation, are not well‐characterized. Catastrophizing is a cognitive and affective process that relates strongly to enhanced reports of pain and that varies as a function of sex. It is thus a prime candidate to explain sex differences; indeed, several prior studies offer evidence that controlling for catastrophizing eliminates the gap between men and women in reported pain. We recruited 198 healthy young adults (115 female) who took part in laboratory studies of pain responses, including thermal pain, cold pain, and ischemic pain, and who also completed questionnaires assessing catastrophizing, mood, and day‐to‐day painful symptoms (e.g. headache, backache). Women reported greater levels of catastrophizing, more recent painful symptoms, and demonstrated lower pain thresholds and tolerances for noxious heat and cold relative to men. Mediational analyses suggested that after controlling for negative mood, catastrophizing mediated the sex difference in recent daily pain but did not mediate the much larger sex differences in pain threshold and tolerance. These findings highlight the role of catastrophizing in shaping pain responses, as well as illuminating potentially important differences between experimental pain assessment and the clinical experience of pain.