book, page-204

As with democracy, I put 'the placebo effect', in the same category. A flawed system but the best we have got.

The placebo effect represents the power of the mind (aka belief) and in any clinical trial it has two principal components being, the individual concerned and the average underlying base potential of belief to alter the course of a particular treatment. (i.e. the combined effect of the individual's strength of belief multiplied by base potential of the treatment to be susceptible to belief.)

In a blinded trial we must remember that the placebo effect will potentially apply to both arms (no one knows whether they are active or not). Provided the strength of the indivuduals power to believe is distributed randomly between the two arms (a function of trial numbers) it can be assumed that it is distributed evenly between the two arms.

Thus the unknown is the base potential of the active treatment to be susceptible to belief which, in a blinded trial applies to both ARMS.

Whether this suits the active or control arm depends then on another important unknown aspect being, the nexus between potential of belief to affect treatment and the actual presence of that treatment.

All right, that was a bit rambling and convoluted, but the take home point is clear. In a blinded trial placebo occurs in both arms and can be more dominant in one arm than the other (i.e. it does not necessarily affect the control arm only).

Placebo, is a function of the brain and pertains to most aspects of human behaviour.