The use of placebo control groups in the assessment of psychiatric drugs: an historical context.

The reliable evaluation of treatments intended for the management of psychiatric illness would not be possible without the use of placebo. Other types of control groups can provide useful information, but none are capable of adducing a finding as compelling and unambiguously interpretable as a statistically significant drug-placebo difference. Its epistemological advantage notwithstanding, the ethicality of employing a placebo control group has been increasingly challenged in recent years. Many who object to the use of placebo on ethical grounds assume, incorrectly, that there are fungible alternatives to the use of placebo in the assessment of psychotropic drugs. This essay attempts to explain, within an historical context, not only why placebo is irreplaceable, but why it is often so difficult to communicate its advantages to those unfamiliar with the epistemological aims and methods of controlled clinical trials.