Perceived cost affects placebo response in Parkinson’s disease
medwireNews: Patients with Parkinson’s disease (PD) may gain a greater benefit from a placebo treatment if they believe it to be expensive, research suggests.
“Our findings complement the well-known patient preference of brand name over generic”, say Alberto Espay (University of Cincinnati, Ohio, USA) and co-researchers.
The 12 study participants, who had moderate to severe levodopa-responsive PD, were told that they were testing two injectable dopamine agonist medications, believed to have similar efficacy but with differing manufacturing procedures that resulted in them having estimated prices of US$ 100 versus US$ 1500 per dose. In fact, they received the same placebo both times.
The patients received the supposedly cheap and expensive drugs in random order, on the same day with a space of 4 hours for the perceived effects to wear off.
Both placebos caused a reduction in symptoms on the United Parkinson’s Disease Rating Scale (UPDRS) part III and, overall, the effect was 9% greater with the expensive than the cheap placebo. The difference was clearest when the expensive placebo was given first, resulting in UPDRS-III scores falling from a baseline of 29.4 to 21.6 with the expensive placebo but just 25.6 with the cheap placebo, which was a significant difference.
Brain imaging findings during an associative learning task also differed according to perceived cost. Expensive placebo, when given first and resulting in improved motor function, caused a slight, nonsignificant decrease in brain activation “in a manner qualitatively similar to levodopa”, which significantly reduced brain activation.
Cheap placebo, by contrast, caused significant brain activation, regardless of whether it was given first or second. If given second, expensive placebo was also associated with increased brain activation, which the researchers attribute to a carryover effect from the cheap placebo.
This suggests “greater brain ‘effort’ (more activity) under placebo conditions of lowered expectations”, writes the team in Neurology.
Patients self-rated their own motor improvements on the Global Clinical Impression (GCI) scale. Expensive placebo caused 66.7% of patients to rate their improvement as very good or marked, compared with 58.3% for cheap placebo. Four patients with negligible responses on the GCI scale claimed, during debriefing when the true nature of the trial was revealed, that they had not particularly expected a treatment benefit.
In an editorial, Peter LeWitt (Henry Ford West Bloomfield Hospital, Detroit, Michigan, USA) and Scott Kim (National Institutes of Health, Bethesda, Maryland, USA) say that the findings “may be bad news for health care providers committed to cost control, especially if such a mindset assumes better results should arise from more expensive drugs.”
They write: “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.”
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