Double-blind Study: Characteristics And Advantages Of This Design

Double blind study

A double-blind study is an experimental method used to ensure impartiality and avoid errors arising from bias of both the participants and the researchers themselves.

Although “classic” studies with a control group and an experimental group work, they are not as safe as double-blind studies, in which not even the researchers themselves know who they are giving the experimental treatment to.

Below we will see in depth how these types of studies work, in addition to reviewing the concept of the placebo effect, its importance in research and how it is controlled.

What is a double blind study?

Double-blind studies are a type of scientific research used to prevent research results from being influenced by the placebo effect, originated in the research participants, and the observer effect, caused by the researchers themselves. These types of studies are very important in numerous fields of research, especially in health sciences and social sciences.

The main aspect of double-blind studies is that both participants and researchers They do not know at first who are the subjects that are part of the experimental group and which subjects are part of the control group.

Thus, researchers do not know which participants are receiving the treatment or condition that they want to know what effects it has and they do not know which participants receive a condition without any effect (placebo).

Blind studies

In scientific research, blind studies are very important tools that allow avoid biases related to the perception of the participants regarding the experimental treatment they receive It is important to understand these types of studies before going into details about double-blind studies, and for this reason to talk at length about what blind studies are like.

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To fully understand how blind studies work, we are going to present a hypothetical case of pharmaceutical research, in which we want to verify the effectiveness of a drug, specifically an antidepressant. We do not know what positive and negative effects this medicine has on health, but what is expected is that it will help raise the mood in people with depression.

100 volunteers with depression are presented to the study. Since we want to know the real effectiveness of this drug, we separate these 100 participants into two groups, with 50 people each. One will be the experimental group, which will receive the antidepressant, while the other will be the control group, which will receive a pill identical to the antidepressant in appearance, but which is actually a placebo, that is, a substance without any type of effect on health.

The reason why half of the participants are not given the antidepressant is, basically, to prevent the placebo effect from biasing the research results. The placebo effect occurs when a person, unconsciously, he notices improvement because he has been told that the treatment he has received has therapeutic power It may not cure at all, but since the person wants it to do so, he begins to notice improvements that are not real.

By creating a control group and an experimental group it is easier to know to what extent the real drug exerts changes, and what specific changes. Any improvement seen in the experimental group that is not observed in the control group will be attributed to the therapeutic power of the experimental drug. In blind studies, no participant knows whether they have received the drug or the placebo, so there is less possibility of fictitious improvements, this being the main advantage of this type of study.

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The problem with this type of study is that Researchers do know which participants receive the real treatment and which receive the placebo treatment This may seem obvious and necessary, but it is also a source of bias. It may be the case that researchers believe they see significant improvements in the experimental group that, in reality, do not exist (observer effect).

Furthermore, it may be that at the time of randomizing the participants, and having some go to the control group and others to the experimental group, the researchers themselves decide to consciously incorporate certain patients because they believe that they have a good chance of improving by receiving the experimental treatment. This is not entirely ethical, since otherwise the results would be “inflated.”

Double-blind studies in more depth

Fortunately, To overcome the limitation of blind studies, there are double-blind studies To avoid the bias attributed to the placebo effect and also the bias attributed to the observer effect, both participants and researchers do not know who makes up the control group and who makes up the experimental group. Because researchers do not know which participants receive the experimental treatment, they cannot attribute improvements to it until they have statistically analyzed the data.

The vast majority of researchers are professionals, there should be no doubt about this. However, There is always the possibility that the researcher may unconsciously alert the participant to the treatment they are receiving, making him discover which group he is a part of. You can even play favorites by giving the treatment to patients who believe they will have a better response, as we have already mentioned.

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Because neither experimenters nor participants know who receives the treatment, the highest level of scientific rigor possible is obtained. The only ones who know who is part of each group are third parties, who will have designed a coding system that will make each participant receive a treatment or not and without the experimenters knowing what they are giving. The researchers will know which people they have given the treatment to when, when studying the data, the codes of each participant are revealed to them.

Returning to the case of the pharmaceutical study, in this case we would have a pill that would be the real drug and another pill that would be the placebo, identical in appearance. Each participant would have received a special code, codes that the researchers would know but would not know what they mean, they would only know that, for example, participant number 001 should be given the pill found in a box with the number 001, and so on. the 100 subjects in the experiment, assuming that 50 will receive the treatment and 50 a placebo.

Once each participant has received the pills, the time stipulated in the experiment is allowed to pass. Once the experiment has been completed and the data of each patient has been collected, they will have reported the changes they have noticed, their physiological state and other measurements, These data will be analyzed statistically It is at this point that the people who have designed the coding system will inform the experimenters who has received the treatment and who has not. This will provide empirical evidence of whether the treatment works or not.