On 15-Oct-99 K.C.Maduako wrote:
> If a placebo is shown to have an effect then it should no longer be
> regarded as such but rather as a bias in the study. If we do not
> restrict our scientific definitions to what they stand for then we
> are not into science and should not pretend to be.
>
> K C Maduako
I think this mis-represents the role of the placebo.
A placebo is a treatment procedure which mimics the procedure for
administering the treatment under trial, but omits whatever components
of the trial treatment are alleged to have the therapeutic effect
(provided this is possible).
As a clear example, the experimental treatment might consist of
administering a capsule containing a drug, while the placebo would
consist of administering an identical capsule containing an inert
substance. Any clear difference between the two can then be attributed
directly to the drug.
This contrasts with a trial in which the "control" group received no
treatment at all. In that case, any clear difference can not be attributed
to the drug as such, since there is the possibility of a "placebo effect".
As I pointed out earlier, if you want to try to disentangle the respective
effects of placebo and treatment, you need to compare a treatment group,
a placebo group, and a group not treated with anything.
However, if you observe no difference between placebo and trial treatment,
this doesn't mean that the allegedly active component of the treatment
is inactive: it could simply mean that, whereas there is a "placebo
mechanism" which causes improvement in cases where the placebo is
given, in cases where the treatment is given a different mechanism
is activated which also causes improvement. The end result for
clinical practice may well be that you can do as well using placebo
as using drug; but, scientifically, you're left in the dark as to what's
going on.
Of course you can't always set up a plausible placebo: quite what
placebo procedure corresponds to extracting a painful tooth eludes
me for the moment.
Best wishes,
Ted.
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E-Mail: (Ted Harding) <[log in to unmask]>
Date: 15-Oct-99 Time: 11:34:39
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