A study compared the effectiveness of several antidepressants by examining the experiments in which they had passed the FDA requirements. Each of those experiments compared
the active drug with a placebo, an inert pill given to some
of the subjects. In each experiment some patients treated with the
placebo had improved, a phenomenon called the placebo effect.
Patients’ depression levels were evaluated on the Hamilton
Depression Rating Scale, where larger numbers indicate greater
improvement. (The Hamilton scale is a widely accepted standard
that was used in each of the independently run studies.) It is well-understood that placebos can have a strong therapeutic effect on depression, but separating the placebo effect from the medical effect can be difficult.