Research suggests that dopamine effects on movement in Parkinson's may be countered by the brain's placebo response.
"Patients' expectations play an important role in the effectiveness of their treatments, and the placebo effect has been well documented, especially in people with Parkinson's disease," explains study author Dr. Alberto Espay.
"We wanted to see if the people's perceptions of the cost of the drug they received would affect the placebo response," adds Dr. Espay, fellow of the American Academy of Neurology (AAN) and associate professor of neurology at the UC Neuroscience Institute of the University of Cincinnati, OH.
Published in the AAN's latest online issue of Neurology, the study is the first in Parkinson's to test the placebo effects of drug cost in a randomized and blinded manner, say the authors. The results show that when people received what they thought was the more expensive drug, motor skills improved by 28% compared with when they received the 'cheap' drug.
In one of the tests of motor skills for the 12 people with Parkinson's disease, scores improved by seven points when they were given what they believed to be an expensive drug - but by only three points when they were told their drug was cheap.
Dr. Espay says the placebo effect may be worth exploiting:
"If we can find strategies to harness the placebo response to enhance the benefits of treatments, we could potentially maximize the benefit of treatment while reducing the dosage of drugs needed and possibly reducing side effects."
The power of deception
The 12 people in the study were told that they would receive two injections for their Parkinson's disease, each a different formulation of the same drug. The second shot would be given after the first shot had worn off, they were told.
The patients were also led to believe that the two formulations were thought to have similar efficacy but different manufacturing cost. They were told one was priced at $100 for each dose while the other cost $1,500 a shot - and that the aim of the study was to prove that, while the drugs were priced differently, they would be equally effective.
Of course, the reality of the study was that the participants received a dummy injection containing just saline solution for both "drugs."
They were told they were receiving either the "cheap" or "expensive" drug first, and underwent several medical tests before and after each of the two placebo shots, including:
- Measures of their motor skills (movements affected by the disorder)
- Scans of brain activity.
On the images produced by MRI (functional MRI, fMRI, during which participants performed tasks), brain activation resembled that seen in the study when the real Parkinson's drug levodopa was used.
Patients 'amazed' by placebo power
Because the study meant deceiving patients about their Parkinson's treatment, it needed strict ethical clearance. The participants were told afterwards about the true nature of the research. Dr. Espay says:
"Eight of the participants said they did have greater expectations of the 'expensive' drug and were amazed at the extent of the difference brought about by their expectations."
"Interestingly," he adds, "the other four participants said they had no expectation of greater benefits of the more expensive drug, and they also showed little overall changes." In other words, there needed to have been an expectation of better results before there was any perception that hopes could indeed hold true.
The reason the placebo effect may be stronger for people with Parkinson's may be related to the disease's effect on brain chemicals, Dr. Espay explains.
The neurological disorder decreases dopamine levels in the brain, while the placebo effect is known to increase the neurotransmitter's release.
Dr. Espay continues his explanation that dopamine - in addition to its role in movement - affects anticipation, motivation and response to new things, adding: "People who receive the shots thinking they received a drug may have an 'expectation of reward' response, which is associated with the release of dopamine similar to the response to the reward itself."
While an accompanying editorial to the study outlines some limitations to the findings, it says: "Taken together, the results indicate that symptomatic actions of placebo on several measurements were modified by price perception, with 'expensive therapy' leading to greater improvement."
The authors of the commentary - from Henry Ford West Bloomfield Hospital's Parkinson's disease and movement disorders center in Detroit, MI - add: "Placebo can be the physician's friend when it enhances therapeutic efficacy. The effects of placebo also can confound clinical trial outcomes or lead to endorsement of worthless treatments. For patients with Parkinson's disease, placebo effect is often robust and enduring."
The neurology experts continue:
"The outcome of this study, despite its limitations, opens our eyes to another nuance of placebo effect with implications for clinical practice, the research enterprise, and health policy."
The study was supported by the Davis Phinney Foundation for Parkinson's, which has produced a self-care management program for people living with the disease, including a set of at-home worksheets covering subjects from exercise and mood to symptoms and clinic visits.
See the Parkinson's hub in MNT's Knowledge Center for more information about the causes, features and management of the disease.
In other news relating to Parkinson's this week, researchers publishing in the same journal Neurology have found difficult Parkinson's symptoms respond to low-frequency deep brain stimulation.
A news story back in November also reported on the way the placebo response specifically affects Parkinson's disease. The study found that placebo boosted brain activity in Parkinson's patients - to the same extent as real medication.