A placebo is a medical treatment with no intended therapeutic value. An example of a placebo is an inert pill, but it can include more dramatic interventions like sham surgery. The placebo effect is the concept that patients will perceive an improvement after being treated with an inert treatment. The opposite of the placebo effect is the nocebo effect, when patients who expect a treatment to be harmful will perceive harmful effects after taking it.
Placebos do not have a physical effect on diseases or improve overall outcomes, but patients may report improvements in subjective outcomes such as pain and nausea. A 1955 study suggested that a substantial part of a medicine’s impact was due to the placebo effect.However, reassessments found the study to have flawed methodology.This and other modern reviews suggest that other factors like natural recovery and reporting biasshould also be considered.
All of these are reasons why alternative therapies may be credited for improving a patient’s condition even though the objective effect is non-existent, or even harmful. David Gorski argues that alternatives treatments should be treated as a placebo, rather than as medicine.Almost none have performed significantly better than a placebo in clinical trials. Furthermore, distrust of conventional medicine may lead to patients experiencing the nocebo effect when taking effective medication.
Regression to the mean
A patient who receives an inert treatment may report improvements afterwards that it did not cause. Assuming it was the cause without evidence is an example of the regression fallacy. This may be due to a natural recovery from the illness, or a fluctuation in the symptoms of a long-term condition. The concept of regression toward the mean implies that an extreme result is more likely to be followed by a less extreme result.
There are also reasons why a placebo treatment group may outperform a “no-treatment” group in a test which are not related to a patient’s experience. These include patients reporting more favourable results than they really felt due to politeness or “experimental subordination”, observer bias, and misleading wording of questions. In their 2010 systematic review of studies into placebos, Asbjørn Hróbjartsson and Peter C. Gøtzsche write that “even if there were no true effect of placebo, one would expect to record differences between placebo and no-treatment groups due to bias associated with lack of blinding.” Alternative therapies may also be credited for perceived improvement through decreased use or effect of medical treatment, and therefore either decreased side effects or nocebo effects towards standard treatment.