Blind experiment

A blind study is a form of an experiment in which the subjects do not know whether they belong to the experimental or the control group. Thus, the influence of expectations and behaviors that would be triggered by this information are eliminated. Blind studies are widely used especially in medical and psychological research; see also ABX test.

Medicine

Basics

In medical efficacy studies people are exposed to in the course of a study either of the tested treatment or the control treatment. In drug trials (ie one to compare to drug or placebo ), one speaks of verum or active substance (that is to be examined medication) or control preparation. Verum and control preparation will be referred to as investigational. The allocation of trial treatment and control treatment is ideally done purely by chance ( randomized).

A study is open when the patients know if they are getting the active treatment or the placebo. In contrast, the study is

• Blindly, if patients do not know which substance (control or active treatment ) they receive ( subject "blind" ).
• Double-blind, if the patient and the treating physician does not know who receives which substance ( test subject and test helpers " blind" ).
• Triple blind if neither the patients nor the treating physician, nor those who carry out the evaluation, to know who gets what substance ( subject, trial helper and Versuchsauswerter "blind" ). Only the sponsor of the study knows who received that substance.

Verblindungstechniken

Important in a blind study is that the drug of the subjects can not be distinguished. The drug should therefore appear visually identical (including the packaging), and also smell and taste play a role.

In order to compare drugs with very different appearances, such as different dosage form, one uses the double-dummy technique. These subjects have two drugs are administered, one of which is a placebo, respectively. For example, a tablet is to be compared with a juice. The patient group received a tablet containing drug and a placebo juice, the comparison group receives a placebo tablet and a juice with active ingredient.

Some medicines are due to their inherent characteristics (eg, bitter taste ) or side effects identify. In order to achieve a reliable blinding here, active placebos would be useful for theoretical reasons, ie substances that trigger only the corresponding side effect. The use of such active placebos occurs, however, rather rare for ethical reasons.

Also, non-pharmacological interventions can be blinding. For example, there are specific acupuncture needles where the needle moves to the actual pressure in an envelope and not pierces the skin.

Scientific journals

In scientific journals submitted research papers are usually not just published, but go through a review process before. Here it is common to use a blind or double-blind opinion. The latter means that the authors do not know who the reviewers, and the reviewers do not know who wrote the articles submitted to them. This is intended to prevent personal preferences and relationships between authors and reviewers have an influence on the assessment of the research contributions.

History

The story of the blind study is closely linked with that of placebo. Placebos were first used in scientific medicine in the 17th century. From this time ( " the true, the right thing" lat ) for the actual medication stems the term " Verum ". In this period, the efficacy of quinine for malaria fever by Thomas Sydenham (1624-1689) has been demonstrated. Therefore, quinine is now regarded as the first verum preparation that has been proven is not a placebo.

The British surgeon James Lind conducted in 1747 for the first time a control medication. He tested at two scurvy the effectiveness of orange juice and lemon juice. One of the patients was given a drink of sea water (placebo), the other the verum.

The first double-blind studies conducted in Central Europe began in the mid-19th century.