The journal of pain : official journal of the American Pain Society
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There is little information regarding changes in placebo responsiveness with age, although first predictors of placebo responders such as psychological and physiological processes have been identified. Reviews and meta-analyses indicate that placebo response rates in randomized controlled trials (RCTs) are higher in children and adolescents compared with adults. As these studies cannot control for age-dependent differences in the natural course of the disease, biases might contribute to different placebo rates in RCTs. To avoid these biases, this study investigated age-related differences in placebo responsiveness between children and adults in a well-established experimental model of placebo analgesia combining classic conditioning and expectation. Our data confirm placebo analgesic responses in children, which did not differ in magnitude from those of adults. The influence of previous experience on subsequent treatment outcome was stronger in children than in adults, indicating an increased relevance of learning processes for treatment outcomes in children. Further studies are needed to understand the influence of treatment-related learning processes in children and adolescents, which might critically determine treatment responsiveness during adulthood. ⋯ This study is the first to experimentally explore placebo analgesia and influences of previous experience on placebo responses in children compared with adults. We found comparable placebo responses in both groups and an increased relevance of learning processes for treatment outcomes in children.
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Data on the tolerability of opioids in patients with cancer-related pain are limited. Here, we report a systematic review that includes all published prospective studies reporting adverse events (AEs) of morphine, oxycodone, fentanyl, methadone, or hydromorphone for cancer-related pain in patients naive for these opioids. We included 25 studies describing 31 treatment cohorts, made an overview of study characteristics, and reported rates of AEs per type of opioid. The frequency of the most commonly reported AEs varied widely: nausea from 3 to 85%, vomiting from 4 to 50%, constipation from 5 to 97%, drowsiness from 3 to 88%, and dry mouth from 1 to 94%. There was a large heterogeneity among included studies, especially regarding the assessment and reporting of AEs. We describe how differences in assessment and reporting influence outcome rates. Although AEs are an important issue in daily clinical practice, realistic incidence rates of AEs per type of opioid are unknown because of the immense heterogeneity among studies. ⋯ Although opioid-related adverse events are an important issue when treating cancer-related pain, realistic rates of adverse events per type of opioid are unknown because of immense heterogeneity among studies and lack of systematic assessment and reporting. There is an urgent need for studies with standardized outcome measures and reporting.
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Many studies have found evidence of conditioning-induced nocebo hyperalgesia. However, these studies have exclusively involved continuous reinforcement (CRF) schedules. Thus, it is currently unknown whether nocebo hyperalgesia can result after partial reinforcement (PRF). We tested this using electrodermal pain stimulation in healthy volunteers. Undergraduates (N = 135) received nocebo treatment under the guise of a hyperalgesic. Participants were randomly allocated to CRF, PRF, or control (no conditioning). Conditioning involved surreptitiously increasing pain stimulation on nocebo trials relative to control trials. During training, the CRF group always had the nocebo paired with the surreptitious pain increase, whereas the PRF group experienced the increase on only 62.5% of nocebo trials. In the test phase, pain stimulation was equivalent across nocebo and control trials. PRF was sufficient to induce nocebo hyperalgesia; however, this was weaker than CRF. Nocebo hyperalgesia failed to extinguish irrespective of the training schedule. Additional assessment of expectancies indicated strong concordance between expectancy and nocebo hyperalgesia. Overall, these findings suggest that once established, nocebo hyperalgesia may be difficult to disrupt. PRF may be a novel method of reducing the intensity of nocebo hyperalgesia in the clinic, which may be particularly important given its persistence. ⋯ This study provides novel evidence that partial reinforcement results in weaker nocebo hyperalgesia than continuous reinforcement and that nocebo hyperalgesia fails to extinguish, irrespective of the training schedule. As a result, partial reinforcement may serve as a method for reducing the intensity of nocebo hyperalgesia in the clinic.
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Validation of the Hospital Anxiety and Depression Scale (HADS) in Patients with Acute Low Back Pain.
The Hospital Anxiety and Depression Scale (HADS) is a self-report instrument used to evaluate depression and anxiety in clinical research. The HADS has advantages over other assessments of anxiety and depression; it is efficient in assessing both anxiety and depression with a total of 14 items, and it was originally developed on a general medical rather than psychiatric sample. However, the HADS has not been evaluated specifically for use in clinical trials of acute pain. Validation analyses were conducted on data from a randomized, double-blind, parallel-group study of tapentadol immediate release vs oxycodone immediate release for acute low back pain (N = 666). Analyses of psychometric properties, internal consistency, convergent validity, assessments of bias, and confirmatory factor analysis were conducted on pretreatment data. Additional analyses were performed to test the responsiveness and predictive validity of the HADS. Both the Anxiety and Depression subscales (1) showed good psychometric properties, (2) had high internal consistency, (3) displayed good convergent validity, (4) had no unexpected biases, (5) fit the a priori factor structure, and (6) were highly sensitive to changes as a result of analgesic treatment. We conclude that the HADS is a valid instrument for efficient, low-burden assessment of anxiety and depression in clinical trials with an acute low back pain population. ⋯ Considered together with the results of other recent studies, the data suggest that the HADS can provide a valid, responsive, and efficient assessment of anxiety and depression in acute low back pain for clinical trials and other clinical research examining acute pain populations.
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There is a growing emphasis in the pain literature on understanding the following second-order research questions: Why do psychosocial pain treatments work? For whom do various treatments work? This critical review summarizes research that addresses the latter question and proposes a moderation model to help guide future research. A theoretical moderation framework for matching individuals to specific psychosocial pain interventions has been lacking. However, several such frameworks have been proposed in the broad psychotherapy and implementation science literature. Drawing on these theories and adapting them specifically for psychosocial pain treatment, here we propose a Limit, Activate, and Enhance model of pain treatment moderation. This model is unique in that it includes algorithms not only for matching treatments on the basis of patient weaknesses but also for directing patients to interventions that build on their strengths. Critically, this model provides a basis for specific a priori hypothesis generation, and a selection of the possible hypotheses drawn from the model are proposed and discussed. Future research considerations are presented that could refine and expand the model based on theoretically driven empirical evidence. ⋯ The Limit, Activate, and Enhance model presented here is a theoretically derived framework that provides an a priori basis for hypothesis generation regarding psychosocial pain treatment moderators. The model will advance moderation research via its unique focus on matching patients to specific treatments that (1) limit maladaptive responses, (2) activate adaptive responses, and (3) enhance treatment outcomes based on patient strengths and resources.