Double blind studies seek to confirm or deny the effectiveness of a treatment by creating conditions in which neither the researcher nor the subject knows whether he is receiving a real product or treatment, or simply receiving a placebo. There are many treatments for various ailments that are completely worthless. Double blind studies attempt to sort through the factors that lead to a treatment becoming recognized and accepted despite the fact that it does not actually perform as believed.
Placebo Effect
Double blind trials seek to reduce or eliminate the possibility that the treatment's effectiveness is due to the placebo effect. The mind has tremendous power over the body. Patients often experience relief of their symptoms even when the treatment they receive is fake. Patients in a study of arthroscopic knee surgery reported such dramatic reductions in pain that they recommended the procedure to their friends, even though no surgery had been performed. "While it's often reported that only 30 percent of people respond to placebo...the response rate seen in some of the conditions I just listed (menopausal hot flashes, symptoms of prostate enlargement and many types of pain) reaches as high as 70 percent," says Dr. Steven Bratman, in an article published on Mendosa.com, a website on diabetes.
Observer Bias
Practitioners can influence the results of the study without intending to do so. Those who knew which patients were receiving real treatments were more likely to note improvement in the subject's condition, although the patient's symptoms had not actually changed. Practitioners often showed more enthusiasm via tone of voice and body language when dealing with a subject who they believed was receiving an effective treatment. Double blind studies are arranged so that neither the practitioner nor the subject knows for certain what treatment, if any, they are receiving.
Reinterpretation
If convinced that they are receiving an effective treatment, some subjects will report a decrease in symptoms, even when it is not true. A patient with a cough might report breathing easier and coughing less, but an observation would reveal that the patient is still coughing just as often. Reinterpretation is an expression of the placebo effect. The subject discounts symptoms or fails to note them, because he expects not to experience them.
Self-Limiting Illness
In a well-designed double blind study, an ineffective treatment and a placebo will have nearly equal effectiveness, or the treatment will be even less effective than the placebo. Some illnesses, especially those caused by viruses, improve on their own with the passage of a given amount of time, no matter whether the illness is treated or not. Flu is a good example of a self-limiting illness. Most flu symptoms arise within 24 hours to three weeks of exposure, and go away within three days to three weeks. Palliatives, such as chicken soup, over-the-counter flu medications, vitamins and herbal remedies provide comfort, but double blind studies show that they do not make significant changes in the course of the illness. The one exception so far is zinc tablets, which do reduce the course of a cold by about three days.
Regression
A well-designed double blind study will weed out instances of regression, the retreat or seeming reduction of symptoms due to a disease already being at its worst. When a chronic illness is treated while it is at its worst, any improvement is often attributed to the treatment, rather than the fact that the symptoms have become less intense on their own. Anything that is already at its worst will automatically appear to be getting better as symptoms decrease. This is one reason why children with progressive diseases such as cystic fibrosis will appear to rally after an experimental treatment.
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