J Manipulative Physiol Ther. 1999 Sep; 22(7): 436-43.

Preliminary study of the effects of a placebo chiropractic treatment with sham adjustments.

Hawk C, Azad A, Phongphua C, Long CR.

Palmer Center for Chiropractic Research, Davenport, Iowa 52803, USA.

OBJECTIVE: To identify aspects of the delivery of placebo chiropractic treatments by using sham adjustments that may cause a treatment effect and that may affect the success of blinding. DESIGN AND SETTING: Two-period crossover design in a chiropractic college research clinic. SUBJECTS: Eighteen volunteer staff, students, and faculty of the chiropractic college who reported low-back pain within the last 6 months. INTERVENTIONS: Flexion-distraction technique was used to perform chiropractic adjustments, and a hand-held instrument (Activator adjusting instrument) with the pressure gauge set on the 0 was used to perform sham adjustments. The treatment period was 2 weeks, with a total of 4 visits. MAIN OUTCOME MEASURES: The Visual Analog Scale (VAS) for pain and Global Well-Being Scale (GWBS). RESULTS: Although VAS and GWBS scores improved with both treatments, a somewhat greater improvement occurred in most cases with the active treatment. Eight of 14 patients interviewed believed that the placebo had a treatment effect. CONCLUSION: This study provided preliminary information that was useful in planning the protocol for a placebo chiropractic treatment in the randomized clinical trial for which it was designed.