There’s a new twist on the well-established placebo effect. The perception you have of a drug’s cost may affect the benefit you receive from taking it.

The study which reached that conclusion appeared in the January 28 online edition of Neurology, the medical journal of the American Academy of Neurology.

Study author Alberto Espay, MD—an associate professor at the University of Cincinnati (UC) Department of Neurology and Rehabilitation Medicine, and director of the James J. and Joan A. Gardner Center for Parkinson’s Disease and Movement Disorders at the UC Neuroscience Institute—explained the study’s purpose this way:

“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. We wanted to see if the people’s perceptions of the cost of the drug they received would affect the placebo response.”

How the study worked

Researchers told 12 people with Parkinson’s that they would receive two injections to treat their disease, and that the two shots were different formulations of the same drug. The second injection would come after the effects of the first had worn off.

The 12 believed that the two shots would have identical efficacies and that, because of manufacturing costs, only their price tags differed significantly. Study leaders told them that one injection cost $100 per dose, while the other one cost $1,500 per dose. Before both injections, subjects were told which type they were getting.

Of course, the “cheap” and the “pricey” injections were identical saline solutions.

To make sure the order of injections—$100 then $1,500—didn’t affect the subjects’ perception of effectiveness, some of them got the cheaper one first. Others received the pricier injection first.

Before and after both placebo injections, researchers tested the subjects to measure their motor skills affected by Parkinson’s, and conducted MRIs to assess brain activity.

Expectation drives perception

During the post-study debriefing, eight of the 12 subjects said they expected the costlier drug to work better, and—as a result—their motor skills improved significantly more than they did after the “cheaper” injection was administered.

The remaining four subjects did not expect the pricier drug to work better, taking to heart the information they had received about the two injections’ similar effectiveness. As a result, they didn't show dramatic differences in motor skills after the two different injections.

Over baseline results—test scores taken before the injections—both placebos improved subjects’ motor skills, regardless of their price/effectiveness expectations. In one of the motor skills tests, scores improved by seven points when subjects received the “expensive” placebo, but only by three points when they got the “cheap” one.

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Additionally, MRI scans correlated with motor skills test results. Brain activity increased after both placebos, and also increased according to efficacy expectation based on cost.

The Parkinson’s/placebo connection

People with Parkinson’s are especially susceptible to powerful placebo effects. While the neurological disorder decreases the level of dopamine in the brain, the placebo effect works to increase it. In addition to its key role in movement (Parkinson’s disease’s depletion of dopamine diminishes—sometimes disables—the brain’s ability to coordinate with the body), dopamine also affects anticipation, motivation, and response to new things. Study leader Espay wrote: "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."

If dopamine depletion in the body is already in play, the dopamine-boosting placebo effect can be disproportionally powerful.

The study report was accompanied by an editorial written by doctors from Henry Ford West Bloomfield Hospital's Parkinson's Disease and Movement Disorders Center in Detroit, MI. According to its authors:

“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 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.”