http://scienceblogs.com/gregladen/2010/10/does_it_matter_whats_in_a_plac.php"Yes, it does matter what is in a placebo (as well as how it is administered, and so on) because the placebo is an important part of the experimental protocol used in pharmaceutical research. Before we get to why this question has even been raised, and an interesting point or two about it, lets quickly cover what a placebo really is.
A placebo is a tool used for making a control in an experiment. So what is a control? A control is a subset of individual variates (which may be people, or samples of some kind, or whatever) that is given a "treatment" that is just like the treatment you are testing out but missing the critical part(s) of the experiment. The control has two closely related purposes (the importance of each will vary): 1) To provide a baseline with which to compare the results of the experiment and 2) to subject the experimental variate (the person, the sample, the whatever) to things that are not part of what you are testing but that happen anyway because you are doing the experiment.
For instance, if your experiment is on humans and it requires that the humans show up at your lab for 10 minutes to have the experiment run on them, you need to rule out that some aspect of coming to your lab for 10 minutes is not the cause of whatever effect you measure. Perhaps you will be bombarding the test subject with rays from a machine you've invented. Well, what if your graduate students are playing around with test versions of this machine all the time so your lab tends to be bathed in the rays. Just showing up will cause anyone to be bombarded with rays, so the specific doses and methods you are using on your test subject may not be sufficiently distinct. So if you have your "controls" (a subset of your test subjects) show up and hang around for 10 minutes and leave with no treatment, you would be catching this problem.
A placebo is a special subset of control conditions where things that you think might result in a faux version of the desired effect are invoked. In the above case you may think that there is a psychological effect, where a subject who thinks they were bombarded with rays (but was not) will give a more positive assessment of their state of being afterwords than otherwise. they will say the pain from their condition is reduced, thinking that the rays must have worked. So, bombarding the patient with fake rays would be a placebo.
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This is a mildly interesting follow-up to this study:
http://www.annals.org/content/153/8/532.abstract , as well as to a ridiculous quack extrapolation made by one of the Internet's biggest quacks. (Links to that can be found at the full article. I won't post them.)
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It's likely that there will be more discussion on this topic in the coming days and weeks. I look forward to it.
:hi: