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In your article, the possibility is mentioned that patients with Parkinson’s disease might have improved in the study because of the placebo effect rather than the administration of the protein glial-cell-line-derived neurotrophic factor. The article then says, “However, brain scans of these patients . . . showed that dopamine supplies in the putamen improved over that time,” seemingly suggesting that such an increase in dopamine would not be likely to occur if the improvement were due to the placebo effect. But it seems entirely plausible and even likely, given that Parkinson’s is caused by low dopamine levels, that the placebo effect would work through increased dopamine levels. To say otherwise seems dangerously close to saying, “The patients’ health improved; therefore the placebo effect was not responsible for their improvement,” which would, of course, be nonsense.

Ben Haller
Redwood City, Calif.