Researchers told 12 patients with Parkinson’s disease that they were testing two drugs, one costing $100 and one $1,500 per dose. The drugs contained the same dose of the same medicine, they explained, but the manufacturing processes were different, and they wanted to see if they worked equally well. The study was published by the journal Neurology.
What the subjects did not know is that they all received an identical injection of a plain saline solution.
The “expensive” placebo worked significantly better, producing a two-fold improvement compared with the “cheap” one. The effect was apparent not only in tests of physical ability, but also as measured by brain imaging. In fact, the effect of the expensive placebo was not significantly different from that of levodopa, the most effective medication for Parkinson’s disease. Levodopa acts by raising levels of the neurotransmitter dopamine in the brain.
“One of the reasons why the effect is so large is that it’s mediated by dopamine,” said the lead author, Dr. Alberto J. Espay, an associate professor of neurology at the University of Cincinnati. “We make more dopamine when we have heightened expectations of efficacy.”
When the subjects were told the true nature of the study, the researchers write, the reactions ranged from incredulity to astonishment.
By extension, are there similar differences in the efficacy of ‘cheap’ vs ‘expensive’ psychiatric medications? ‘Gold standard’ vs ‘novel’ vs ‘run-of-the-mill’ varieties of medications? How much do some factors (eg a patient’s expectation of a particular drug’s therapeutic efficacy, the opinions of other users etc) play a role in treatment outcomes?