Frequency and circumstances of placebo use in clinical practice - a systematic review of empirical studies

Background: The use of placebo interventions outside clinical
trials is ethically, professionally and legally controversial.
Little is known about the frequency and circumstances of placebo
use in clinical practice. Our aim was to summarize the available
empirical studies addressing these issues. Methods: We searched
PubMed and EMBASE from inception to July 2009 in order to identify
cross-sectional surveys, qualitative or longitudinal studies among
health care professionals, students or patients which investigated
at least one of the following issues - frequency of placebo use or
attitudes to, or motivations for, the use of placebo interventions.
At least two reviewers extracted information on the study methods,
participants and findings. Descriptive summaries were prepared in
an iterative process by at least two reviewers per study. Results:
Twenty-two studies from 12 different countries met the inclusion
criteria. Most studies had relevant shortcomings. The proportion of
respondents reporting that they had applied `pure' placebos (for
example, saline injection) during their professional life varied
between 17% and 80% among physicians and between 51% and 100% among
nurses, but it seems that the actual frequency of such use seems to
be rare. The use of `impure' or `active' placebos (for example,
antibiotics for viral infections) is likely to be much more
frequent. However, it is impossible to make a reliable estimation
because there is no agreement of what an impure placebo might be.
Studies using qualitative methods or asking participants to judge
case examples suggest that motivations and attitudes towards
placebo use are complex and health care providers are often faced
with a dilemma. Conclusions: Although the available evidence is
incomplete and confusing at times there can be little doubt that
the prevalence of placebo use outside of clinical trials is not
negligible and that views and attitudes on placebos use differ
considerably among individuals, both health care professionals and
patients. Further research is needed to clarify these issues.