Components of placebo effect: randomised controlled trial in patients with irritable bowel syndrome.
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.


METHODS
A six week single blind three arm randomised controlled trial.


METHODS
Academic medical centre.


METHODS
262 adults (76% women), mean (SD) age 39 (14), diagnosed by Rome II criteria for and with a score of > or =150 on the symptom severity scale.


METHODS
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.


METHODS
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.


CONCLUSIONS
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.


BACKGROUND
Clinical Trials NCT00065403.
Kaptchuk
Ted J
TJ
Osher Research Center, Harvard Medical School, 401 Park Drive, Boston, MA 02215, USA. ted_kaptchuk@hms.harvard.edu
Kelley
John M
JM
Conboy
Lisa A
LA
Davis
Roger B
RB
Kerr
Catherine E
CE
Jacobson
Eric E
EE
Kirsch
Irving
I
Schyner
Rosa N
RN
Nam
Bong Hyun
BH
Nguyen
Long T
LT
Park
Min
M
Rivers
Andrea L
AL
McManus
Claire
C
Kokkotou
Efi
E
Drossman
Douglas A
DA
Goldman
Peter
P
Lembo
Anthony J
AJ
D015670:Acupuncture Therapy / Q000009:adverse effects / Q000379:methods*; D000328:Adult; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000628:therapy*; D008297:Male; D015990:Placebo Effect; D016037:Single-Blind Method; D016896:Treatment Outcome; D014850:Waiting Lists