12 July 2004
Placebo Surgery Shows Surprising Results
by Kate Melville
Research by Doctor Cynthia McRae of the University of Denver's College of Education provides strong evidence for a significant mind-body connection among patients who participated in a Parkinson's surgical trial.
Forty persons from the United States and Canada participated to determine the effectiveness of transplantation of human embryonic dopamine neurons into the brains of persons with advanced Parkinson's disease. Twenty patients received the transplant while 20 more were randomly assigned to a sham surgery condition. Dr. McRae reports that the "placebo effect" was strong among the 30 patients who participated in the quality of life portion of the study.
"Those who thought they received the transplant at 12 months reported better quality of life than those who thought they received the sham surgery, regardless of which surgery they actually received," says Dr. McRae. More importantly, objective ratings of neurological functioning by medical personnel showed a similar effect. In the report, appearing in the Archives of General Psychiatry, Dr. McRae writes "medical staff, who did not know which treatment each patient received, also reported more differences and changes at 12 months based on patients' perceived treatment than on actual treatment."
One patient reported that she had not been physically active for several years before surgery, but in the year following surgery she resumed hiking and ice skating. When the double blind was lifted, she was surprised to find that she had received the sham surgery.
Although patient perceptions influenced their test scores, when the total sample of patients was grouped by the actual operation they received, patients who had the actual transplant surgery showed improvement in movement while, on average, patients who had sham surgery did not.
Professor Dan Russell at Iowa State, the study's co-author, says the findings have both scientific and practical implications. "This study is extremely important in regard to the placebo effect because we know of no placebo studies that have effectively maintained the double-blind for at least 12 months. The average length of placebo studies is eight weeks," according to Russell. Dr. McRae notes that similar results related to the placebo effect have been found in other studies with patients with Parkinson's disease. She says that there is a need for placebo controls in studies evaluating treatment for Parkinson's as the placebo effect seems to be very strong in this disease. Dr. McRae also reports that although the sham surgery research design is somewhat controversial and has raised some ethical concerns, the results of this study show "the importance of a double-blind design to distinguish the actual and perceived values of a treatment intervention."