Placebo is usually defined as an inert or innocuous substance (often a chemical agent) that is used in a controlled experiment to test the efficacy of some other agent (often a drug). The so-called "placebo effect" is the observation of the desired effect in the placebo group. Given this background, it is unclear to me how a placebo effect could be an explanation for hormesis. The "placebo" in a controlled experiment to test an hormesis hypothesis would be a sham exposure (i.e., no radiation exposure). If a placebo effect is present, then a beneficial health effect would be observed in the unexposed group. This might suggest that psychological and/or other factors unrelated to radiation may be important but would not be helpful in elucidating mechanisms of radiation hormesis.] Placebo effects in drug trials are very common. Such effects complicate interpretation of real drug effects and also suggest that psychosocial, spiritual and other factors can seriously affect the results of treatment.
Kenneth L. Mossman
Professor of Health Physics
Director, Office of Radiation Safety
Arizona State University
Tempe, AZ 85287-3501
Voice: 480.965.6190
Fax: 480.965.6609
Cell: 602.769.2371
E-mail: ken.mossman@asu.edu