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Objective To investigate whether placebo effects can experimentally be separated into the response to three components—assessment and observation, a therapeutic ritual (placebo treatment), and a supportive patient-practitioner relationship—and then progressively combined to produce incremental clinical improvement in patients with irritable bowel syndrome. To assess the relative magnitude of these components. Design A six week single blind three arm randomised controlled trial. Setting Academic medical centre. Participants 262 adults (76% women), mean (SD) age 39 (14), diagnosed by Rome II criteria for and with a score of ≥150 on the symptom severity scale. Interventions For three weeks either waiting list (observation), placebo acupuncture alone (“limited”), or placebo acupuncture with a patient-practitioner relationship augmented by warmth, attention, and confidence (“augmented”). At three weeks, half of the patients were randomly assigned to continue in their originally assigned group for an additional three weeks. Main outcome measures Global improvement scale (range 1-7), adequate relief of symptoms, symptom severity score, and quality of life. Results At three weeks, scores on the global improvement scale were 3.8 (SD 1.0) v 4.3 (SD 1.4) v 5.0 (SD 1.3) for waiting list versus “limited” versus “augmented,” respectively (P<0.001 for trend). The proportion of patients reporting adequate relief showed a similar pattern: 28% on waiting list, 44% in limited group, and 62% in augmented group (P<0.001 for trend). The same trend in response existed in symptom severity score (30 (63) v 42 (67) v 82 (89), P<0.001) and quality of life (3.6 (8.1) v 4.1 (9.4) v 9.3 (14.0), P<0.001). All pairwise comparisons between augmented and limited patient-practitioner relationship were significant: global improvement scale (P<0.001), adequate relief of symptoms (P<0.001), symptom severity score (P=0.007), quality of life (P=0.01).Results were similar at six week follow-up. Conclusion Factors contributing to the placebo effect can be progressively combined in a manner resembling a graded dose escalation of component parts. Non-specific effects can produce statistically and clinically significant outcomes and the patient-practitioner relationship is the most robust component. Trial registration Clinical Trials NCT00065403.
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Little is known about placebo effects with scientific precision. Poor methodology has confounded our understanding of the magnitude and even the existence of the placebo effect. Investigating placebo effects presents special research challenges including: the design of appropriate controls for studying placebo effects including separating such effects from natural history and regression to the mean, the need for large sample sizes to capture expected small effects, and the need to understand such potential effects from a patient's perspective. This article summarizes the methodology of an ongoing NIH-funded randomized controlled trial aimed at investigating whether the placebo effect in irritable bowel syndrome (IBS) exists and whether the magnitude of such an effect can be manipulated to vary in a manner analogous to “dose dependence.” The trial also uses an innovative combination of quantitative and qualitative methods.
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