Methodology

Blind trials

Things like sugar pills, that look like real treatments but in fact have no physical effect are used to create "blind" trials in which the participants do not know whether they are getting the active treatment or not, so that physical effects can be measured independently of the participants' expectations. Blind trials control all of these by making whatever expectations there are equal for all cases.

Placebos are not the only possible technique for creating "blindness" (= unawareness of the treatment): to test the effectiveness of prayer by others, the participants are not told who has and has not had prayers said for them. To test the effect of changing the frequency of fluorescent lights on headaches. the light fittings are changed at night in the absence of the office workers (this is a real case). It has been shown that "mock" surgery can have similar effects,Script error: No such module "Unsubst". and so some surgical techniques must be studied with placebo controls (rarely double blind, due to the difficulty involved).

Double-blind trials

Because a doctor's belief in the value of a treatment can affect his or her behavior, and thus what his or her patient believes, clinical trials are usually conducted in "double-blind " manner: that is, not only are the patients made unaware when they are receiving a placebo, the doctors are made unaware too.

Nearly all studies conducted find benefit in the placebo group. For example, Khan published a meta-analysis of studies of investigational antidepressants and found a 30% reduction in suicide and attempted suicide in the placebo groups and a 40% reduction in the treated groups. [5] However, studies generally do not include an untreated group, so determining the actual size of the placebo effect, compared to totally untreated patients, is difficult.

Natural history groups

The practice of using an additional natural history group as the trial's so-called "third arm " has emerged; and trials are conducted using three randomly selected. equally matched trial groups, David [6] wrote: ". it is necessary to remember the adjective ‘random’ [in the term ‘random sample’] should apply to the method of drawing the sample and not to the sample itself. ".

The Active drug group (A ): who receive the active test drug. The Placebo drug group (P ): who receive a placebo drug that simulates the active drug. The Natural history group (NH ): who receive no treatment of any kind (and whose condition, therefore, is allowed to run its natural course).

The outcomes within each group are observed, and compared with each other, allowing us to measure:

The efficacy of the active drug's treatment. the difference between A and NH (i. e. A-NH ). The efficacy of the entire treatment process alone: the difference between P and NH (i. e. P-NH ). The efficacy of the active drug's active ingredient. the difference between A and P (i. e. A-P ). The magnitude of the placebo response. the difference between P and NH (i. e. P-NH ).

It is a matter of interpretation whether the value of P-NH indicates the efficacy of the entire treatment process or the magnitude of the "placebo response". The results of these comparisons then determine whether or not a particular drug is considered efficacious.

"Talking therapies" (such as hypnotherapy. psychotherapy. counseling, and non-drug psychiatry ) are now required to have scientific validation by clinical trial. However, there is controversy over what might or might not be an appropriate placebo for such therapeutic treatments. In 2005, the Journal of Clinical Psychology. devoted an issue to the issue of "The Placebo Concept in Psychotherapy " that contained a range of contributions to this question.

Indexing

In certain clinical trials of particular drugs, it may happen that the level of the "placebo responses" manifested by the trial's subjects are either considerably higher or lower (in relation to the "active" drug's effects) than one would expect from other trials of similar drugs. In these cases, with all other things being equal. it is reasonable to conclude that:

the degree to which there is a considerably higher level of "placebo response" than one would expect is an index of the degree to which the drug's active ingredient is not efficacious . the degree to which there is a considerably lower level of "placebo response" than one would expect is an index of the degree to which, in some particular way, the placebo is not simulating the active drug in an appropriate way.

However, in particular cases such as the use of Cimetidine to treat ulcers, a significant level of placebo response can also prove to be an index of how much the treatment has been directed at a wrong target.