The impact of psychological factors on placebo responses in a randomized controlled trial comparing sham device to dummy pill.

OBJECTIVES: To explore to what extent psychological factors such as expectation, depression, anxiety and belief in alternative medicine impact placebo response and differential responses to separate placebo interventions. METHODS: We analysed data from a randomized controlled trial designed to compare the clinical response of two distinct placebo treatments (sham acupuncture device and placebo pill) in 119 participants with persistent distal upper arm pain due to repetitive stress injury. We used a multivariable linear regression model to identify potential correlates of self-reported upper extremity pain at the end of treatment in both placebo arms of the study combined. We also performed stratified analyses by placebo treatment. RESULTS: We did not find any of the psychological factors of interest to be associated with pain at the end of treatment in our combined analysis. We found higher baseline pain score and pain for longer than 1 year's duration to be significantly associated with higher pain scores at the end of treatment for the placebo treatments combined. In stratified analyses, for the sham acupuncture group, we found higher baseline depression score, higher baseline pain score and younger age to be independently correlated with higher pain score at the end of treatment. For the placebo pill group, only baseline pain was significantly correlated to pain score at the end of treatment. CONCLUSION: In this trial, neither expectancy nor psychological states were associated with response to placebo, with the exception of baseline depression score for the sham acupuncture arm.

Sham device v inert pill: randomised controlled trial of two placebo treatments.

OBJECTIVE: To investigate whether a sham device (a validated sham acupuncture needle) has a greater placebo effect than an inert pill in patients with persistent arm pain. DESIGN: A single blind randomised controlled trial created from the two week placebo run-in periods for two nested trials that compared acupuncture and amitriptyline with their respective placebo controls. Comparison of participants who remained on placebo continued beyond the run-in period to the end of the study. SETTING: Academic medical centre. PARTICIPANTS: 270 adults with arm pain due to repetitive use that had lasted at least three months despite treatment and who scored > or =3 on a 10 point pain scale. INTERVENTIONS: Acupuncture with sham device twice a week for six weeks or placebo pill once a day for eight weeks. MAIN OUTCOME MEASURES: Arm pain measured on a 10 point pain scale. Secondary outcomes were symptoms measured by the Levine symptom severity scale, function measured by Pransky's upper extremity function scale, and grip strength. RESULTS: Pain decreased during the two week placebo run-in period in both the sham device and placebo pill groups, but changes were not different between the groups (-0.14, 95% confidence interval -0.52 to 0.25, P = 0.49). Changes in severity scores for arm symptoms and grip strength were similar between groups, but arm function improved more in the placebo pill group (2.0, 0.06 to 3.92, P = 0.04). Longitudinal regression analyses that followed participants throughout the treatment period showed significantly greater downward slopes per week on the 10 point arm pain scale in the sham device group than in the placebo pill group (-0.33 (-0.40 to -0.26) v -0.15 (-0.21 to -0.09), P = 0.0001) and on the symptom severity scale (-0.07 (-0.09 to -0.05) v -0.05 (-0.06 to -0.03), P = 0.02). Differences were not significant, however, on the function scale or for grip strength. Reported adverse effects were different in the two groups. CONCLUSIONS: The sham device had greater effects than the placebo pill on self reported pain and severity of symptoms over the entire course of treatment but not during the two week placebo run in. Placebo effects seem to be malleable and depend on the behaviours embedded in medical rituals.