Strong Placebo, Strong Parkinson's Effect
Surprisingly, Patients Improve Just From Thinking They Had Surgery
April 14, 2004 --- An extreme placebo treatment -- brain surgery -- had a strong positive effect on Parkinson's patients.
The unusual clinical trial, first reported in 2001, looked at whether transplants of embryonic brain cells could help people with Parkinson's disease. All 39 people in the study had four holes drilled in their skulls under local anesthesia. Half of them actually got the transplants. The other half received sham surgery -- meaning patients received no treatment other than having holes drilled.
Thirty of the patients agreed to participate in a quality-of-life study after the surgery. As part of the study, they were asked whether they thought they got the transplant or placebo.
"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," researcher Cynthia McRae, PhD, of the University of Denver, says in a news release.
Moreover, doctors -- who did not know which surgery the patients got -- also rated these patients as doing better. The findings appear in the April issue of Archives of General Psychiatry.
Among the 30 participants in the quality-of-life study, those who thought they received brain-cell transplants did better, as a group, than those who actually received the treatment (in the overall study, objective measures of patient function showed that the transplants offered some benefit to younger Parkinson's patients).
"Individuals desperate enough for relief from symptoms to risk the conditions of this study may have been inclined to imagine themselves getting better over time, particularly when they did not really know what 'getting better' might look like," McRae and colleagues write.
Some of the placebo patients, however, made striking improvements. One patient said she had not been physically active for several years before surgery. After surgery, she was able to hike and ice skate. She eventually learned she'd had sham surgery.
"Research indicates that the more extreme the placebo treatment is in a clinical trial, the more susceptible participants are to the placebo effect, or believing that they are being helped by the sham medication or treatment," McRae and colleagues note. "This study involved brain surgery -- arguably an extreme placebo treatment. ... The results are consistent with a strong placebo effect."
The researchers say the study results show the need for comparison groups in Parkinson's studies.