Are Double-Blind Experiments Valid?

Why the Results of Double-Blind Studies are Suspect^*

Double-blind, placebo-controlled experiments are widely regarded by the scientific community to be the most legitimate method of testing the efficacy of pharmaceuticals. In fact, the effectiveness of a potential medication is not considered to have been adequately demonstrated unless it is so tested. A double-blind experiment is one in which neither the subjects nor the experimenter knows to whom the actual drug or placebo* has been administered. The reason for this reciprocal concealment is that every scientific experiment requires a control group, which is treated the same in every respect as the experimental group except in that the control group does not receive the active principle to be tested. It is accepted that double-blind experiments are a scientific way of correcting for the placebo effect.

The problem is, if the placebo effect is real, then a drug that has any noticeable side effects will have a greater stimulation of that effect than will the sugar pill. Therefore the placebo effect is stronger for the group receiving the drug than for the group receiving the placebo. It would seem that this fact makes the experiment invalid. In order for the experiment to be valid, the placebo should not be made of just sugar but have all of the effects of the pharmaceutical other than the “beneficial” effect. Of course, this modification is seldom done (if at all).

One possible result is that drugs with a lot of side effects are more likely to pass the double-blind, placebo-controlled experiment than those that have milder side effects. If this conjecture is valid, then the double-blind, placebo-controlled experiment would seem to create an advantage for drugs with more rather than less side effects.

*A placebo is a pseudo medication, consisting of non-active principle, which, in scientific studies, is administered to a control group of subjects to distinguish the true effects of the active principle, given to another group of subjects, from spurious effects that may arise from spontaneous or psychosomatic recovery (the so-called placebo effect).

^*From Robert Chuckrow, The Intelligent Dieter’s Guide, Rising Mist Publications, Briarcliff Manor, NY, 1997.