The placebo effect and double-blind research studies

If you read our blog regularly, you undoubtedly have noticed that frequently, when we describe a research study, we report something like: half the participants in the study had such-and-such a treatment and the other half were given a placebo (or no treatment).

Placebos in studies are important. We try to choose the best research studies to report here, and the best research studies are the ones that are “double-blind placebo-controlled trials”. We avoid presenting studies that do not use a placebo.

Placebo, which comes from Latin “I will please”, is a pill or treatment that is inert; meaning, it should have no real effect on the body at all. For example, if researchers are trying to see if a new medication has an effect, they will typically give half the study participants the new medication and the other half a pill that looks and tastes and has the consistency exactly—or as close as possible—like the real pill.

But using a placebo alone is not good enough. To make research as honest as possible, and free from bias, the study should be “double-blind”. This means neither the participants in the study, nor the researchers themselves know if a participant is getting the real drug or the placebo. The code is broken to identify who received what, only at the end of the study. This is critical to decrease the chance of bias by the researcher.

This sort of bias is very possible, particularly for studies sponsored by drug companies who are hoping that the new drug really has the hoped-for effect. If the study is not “double-blind”, there is too much temptation to skew the results in favor of the drug.

But why is a placebo even necessary?  Because of the “placebo effect”, meaning: people taking a pill or treatment (including a surgical treatment) want, on some subconscious level, for the treatment to work, to be effective. And just that psychological effect of receiving any treatment, even one that, physiologically, should have absolutely no effect on the person, that person reports some positive effect. Their body, working in some complex interaction with their mind, somehow makes them better.

The percentage of people who get better when given a placebo depends on the type of placebo and what is being treated or studied. For example, the placebo effect in pain or depression studies is often strong, and more people get a positive effect from injection placebos than placebos given by capsule. In general though, about one out of three people seem to have a positive placebo effect in research studies.

Placebos are not necessarily pills or injections. “Fake” acupuncture has been used, even placebo surgery, though rarely. In these, one group undergoes the real surgery and the other group has only an incision made, which is sewn up just like the people who had the complete surgery, and the results of the two groups are compared.

The placebo effect is complex, and it is not fully known why placebos work. But placebos demonstrate the power of the mind-body connection, and we will cover this topic further in the coming weeks.

Should you wish to find a doctor, of any specialty, anywhere in Brazil, use our main website:

See also in ProcuraMed (a study that used “placebo” acupuncture):

*Large study points to efficacy of acupuncture









Should you wish to find a doctor, of any specialty, anywhere in Brazil, use our main website:

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