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McRae C, Cherin E, Yamazaki TG, et al. Effects of Perceived Treatment on Quality of Life and Medical Outcomesin a Double-blind Placebo Surgery Trial. Arch Gen Psychiatry. 2004;61(4):412–420. doi:10.1001/archpsyc.61.4.412
This study was part of a large double-blind sham surgery–controlled
trial designed to determine the effectiveness of transplantation of human
embryonic dopamine neurons into the brains of persons with advanced Parkinson's
disease. This portion of the study investigated the quality of life (QOL)
of participants during the 1 year of double-blind follow-up.
To determine whether QOL improved more in the transplant group than
in the sham surgery group and to investigate outcomes at 1 year based on perceived
treatment (the type of surgery patients thought they received).
Participants were randomly assigned to receive either the transplant
or sham surgery. Reported results are from the 1-year double-blind period.
Participants were recruited from across the United States and Canada.
Assessment and surgery were conducted at 2 separate university medical centers.
A volunteer sample of 40 persons with idiopathic Parkinson's disease
participated in the transplant ("parent") study, and 30 agreed to participate
in the related QOL study: 12 received the transplant and 18 received sham
Interventions in the parent study were transplantation and sham brain
surgery. Assessments of QOL were made at baseline and 4, 8, and 12 months
Main Outcome Measures
Comparison of the actual transplant and sham surgery groups and the
perceived treatment groups on QOL and medical outcomes. We also investigated
change over time.
There were 2 differences or changes over time in the transplant and
sham surgery groups. Based on perceived treatment, or treatment patients thought
they received, there were numerous differences and changes over time. In all
cases, those who thought they received the transplant reported better scores.
Blind ratings by medical staff showed similar results.
The placebo effect was very strong in this study, demonstrating the
value of placebo-controlled surgical trials.
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