Conclusions Regarding the Role of Expectations in Placebo Analgesia Studies May Depend on How We Investigate It: A Meta-Analysis, Systematic Review, and Proposal for Methodological Discussions.
Sigrid Juhl Lunde, Sophie Rosenkjær, Susan Tomczak Matthiesen, Irving Kirsch, Lene Vase
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引用次数: 0
Abstract
Objective: Expectations are highlighted as a key component in placebo effects. However, there are different approaches to whether and how placebo studies should account for expectations, and the direct contribution has yet to be estimated in meta-analyses. Using different methodological approaches, this meta-analysis and systematic review examines the extent to which expectations contribute to pain in placebo studies.
Methods: The databases PubMed, PsycINFO, Embase, and Web of Science were searched for placebo analgesia mechanism studies with numerical measures of both expectations and pain. Thirty-one studies, comprising 34 independent study populations (1566 subjects: patients and healthy participants) were included. Two meta-analyses were conducted: meta-analysis 1, using study-level data, estimated the effect of expectation interventions without taking measures of expectations into account (expectations assumed); and meta-analysis 2, using individual-level data, estimated the direct impact of participants' expectations on pain (expectations assessed). Risk of bias was assessed using the Cochrane risk-of-bias tool.
Results: Meta-analysis 1 showed a moderate effect of expectation interventions over no expectation intervention on pain intensity (Hedges g = 0.45, I2 = 54.19). Based on 10 studies providing individual-level data, meta-analysis 2 showed that expectations predicted pain intensity in placebo and control groups ( b = 0.36, SE = 0.05), although inconsistently across study methodologies.
Conclusions: Participants' expectations contributed moderately to pain in placebo analgesia studies. However, this may largely be influenced by how we measure expectations and how their contribution is conceptualized and analyzed-both within and across studies.
期刊介绍:
Psychosomatic Medicine is the official peer-reviewed journal of the American Psychosomatic Society. The journal publishes experimental, clinical, and epidemiological studies on the role of psychological and social factors in the biological and behavioral processes relevant to health and disease. Psychosomatic Medicine is an interdisciplinary peer-reviewed journal devoted to high-quality science on biobehavioral mechanisms, brain-behavior interactions relevant to physical and mental disorders, as well as interventions in clinical and public health settings.
Psychosomatic Medicine was founded in 1939 and publishes interdisciplinary research articles relevant to medicine, psychiatry, psychology, and other health-related disciplines. The print journal is published nine times a year; most articles are published online ahead of print. Supplementary issues may contain reports of conferences at which original research was presented in areas relevant to the psychosomatic and behavioral medicine.