Placebos are dead, long live placebos

A growing body of research suggests that placebos–inactive substances used as sham medications–can alone improve the health of at least some patients (SN: 2/3/01, p. 74: Medicinal Mimicry). Controversy over that claim intensified after researchers analyzed many past studies and reported in the May 24 New England Journal of Medicine that the so-called placebo effect simply reflects the waxing and waning of disease.

Now, a study provides new evidence for the placebo effect and suggests a mechanism through which placebos might benefit patients with Parkinson’s disease.

People with Parkinson’s disease experience muscle tremors and difficulty moving because they have abnormally low amounts of dopamine in their brains. Researchers from the University of British Columbia in Vancouver were measuring brain dopamine to explore side effects associated with treatments. They were surprised to find that after patients were given a placebo of subcutaneous saline injections, they showed higher dopamine concentrations than they had before the procedure.

Looking carefully at data from six people, the team found an average of 17 percent more dopamine in the brain after a saline injection than before it, says A. Jon Stoessl, who reported the results in the Aug. 10 Science. That’s similar to the response seen when the researchers gave the same patients a drug, apomorphine, known to briefly raise dopamine concentrations in the brain. Levodopa, the most commonly used drug for Parkinson’s, raises dopamine concentrations by about the same amount but for longer periods, says Stoessl.

“This is not a trivial or subtle change,” he notes.

The next step is to study whether the dopamine release after the saline injections improves a patient’s symptoms, says Stoessel. His team didn’t look at it in this study because they knew the dopamine boost from apomorphine or the placebo doesn’t last any longer than the patients’ time in the imaging machine.