'via Blog this'During the wash-out period [a period of 1 to 2 weeks before the study begins where subjects are removed from all existing medications], all patients are given daily placebo pills. Hence, another name for this pre-study period is the “placebo wash-out phase.” Patients whose depressions quickly improve during this time are labeled “placebo responders” and excluded from the actual study. Administering a placebo during the wash-out phase is also a technique used by pharmaceutical companies to wee out patients who would respond quickly to a placebo in the official study. This weakens the performance of the placebo by removing quick placebo responders, thereby making the performance of the antidepressants look better.
Pharmaceutical companies use this technique because the placebo effect accounts for such a high percentage of an antidepressant’s effect. According to the FDA, the placebo effect accounts for about 80% of the effect of antidepressants. [...] If the pharmaceutical companies did not use the placebo wash-out procedure, the difference between placebo and antidepressants would be even smaller. Thus, the placebo wash-out phase accomplishes two tasks: washing out patients’ old drugs and weeding out placebo responders.