Anavex Life Sciences Corp (AVXL)

[Steady_T]

Because an individual has an identified biomarker doesn't really say anything about what placebo response that individual will have. Identifying subjects with a particular biomarker in both treatment and placebo arms allows for a comparison of the two groups to determine if there is a difference. If there is a difference only then is the biomarker validated.

You have identified the reason for a placebo control group. It is unknown what placebo response a group of people will have to the treatment protocol in advance. To find that out a placebo arm of a study is set up.

A placebo control group does more than control for the psychological aspects of a trial. It also controls for many other unknown variables in the trial. For example, may be the disease of interest in the trial responds to the dye used in a scan. Or maybe there is some sort of selection bias in the population selection. Maybe just being in a trial reduces stress enough to cause a response.

I remember a particular rat behavior study from school where that experiment was duplicated in England and the researchers got very different results to overcrowding. After a great deal of testing and research it was discovered that the newspaper used for bedding in the US differed from the newspaper used in England. The English newspaper material was made with a different process and had an estrogen mimicking hormone residue in it that the US paper did not. That Estrogen mimicking hormone caused the difference in rat behavior.

It is that sort of unknown, off the wall, sort of thing that placebo group help account for along with the more obvious things.