A double-blind study is one in
which both, the investigator and the participant, are unaware of the nature of
treatment the participant is receiving. This experimental method is used to
ensure impartiality and eliminate the errors arising from observer
misconceptions or prejudices.
During a research, it is quite possible for an
investigator to consciously or subconsciously influence the experimental
observations. Implementing a double-blind study
provides an extra check.
Researchers are often under pressure from drug companies to generate positive
results. This always gives a chance that scientists might manipulate results in
the fight for research grants, and try to show the study in a better light.
There is also the fear of researchers favoring patients that they think would
have the best chance of recovery, thus skewing the results. Proving that the study has been carried out
as a double-blind experiment reduces the chances of criticism
In a double-blind study, some of the
participants are given the treatment, while others are given placebo medicine
or a standard approved
comparative drug for that condition. The appearance of the medications is
usually the same, so that no one is aware which medication is being
administered to whom. The assignment of study participants to treatment or
control group is done randomly. However,
one of the conditions for implementing this method is that the two compared,
randomly assigned study groups are equal in all respects.
Researchers have suggested that since there can be
multiple causes for a disease, it could affect equal assignment to each study
. For example, consider a study being conducted on
treatment of depression where patients are randomly assigned to two different
medications. Depression is a condition that has multiple causes. Thus, though
all other factors may be equal in the two groups, the causes may vary, thus
interfering with the results.
Using mathematical calculations, the researchers also
suggest that increasing the number of study participants decreases the
probability of getting two equal groups with respect to similar causes of
. Therefore, the researchers advise using an
additional marker in the diagnostic criteria for a disease. For example, for a
trial in pneumonia patients, besides using symptoms as criteria, it would be
better to classify patients based on the microorganism causing pneumonia