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What Kind of Influences Do Informal Trial Characteristics have on the Placebo Effect in Clinical Studies?

Principal Investigators: C. Sadaghiani, PhD; H. Walach, PhD

Affiliations: University Hospital Freiburg, Department of Environmental Medicine and Hospital Epidemiology, Germany; Samueli Institute for Information Biology™

Background: The classical interpretation of placebo effects is that they comprise expectancies determining both cognition and behavior towards improvement of self-efficacy. Besides the fact that placebo effects seem to be omnipresent in clinical trials, there are a series of earlier reports suggesting that improvement rates with placebo can be dependent on the expectation of the experimenters. In a previous investigation, we investigated the Principal investigators of recently published studies by using a short questionnaire. This self-devised form asked for information about the context of the study, especially the importance for the researcher's career and his involvement. The idea was to construct a kind of 'index of experimenter involvement' in order to see whether this was correlated with the study’s outcome. Interestingly, we were unable to confirm this assumption. Since this was a retrospective project, we cannot rely on the validity of the conclusion. In this next step, we will ask Principal investigators of ongoing studies.

Method: We will contact the Principal investigators of ongoing trials and ask them to provide information according to our self-devised questionnaire (10 questions). Inclusion criteria for studies are: only ill adults are treated, and the design is double-blind, placebo-controlled, and randomized. Cross-over studies are excluded. Using correlational and regression analyses we will specify the influence of informal study characteristics (e.g., expectations) on the placebo effect. To do so, we expect at least 100 completed questionnaires.

Results: If our previous findings are replicated, then the expectancy hypothesis alone will be an unlikely explanation for placebo effects.

Relationship to SIIB Mission and Healing: Better understanding of the placebo effect could lead to a clearer distinction between artifacts of the experimental research itself, and the exchange of true information between healer and healee as influencing the healing process. In addition, scientists can have more confidence that the bias of those conducting the research will not influence the study outcome if proper controls for expectancy are implemented.