Answers are grounded in this paper and cite their sources.
A study of 203 depressed outpatients who were randomly assigned to one of seven active drug treatment groups or to a placebo group demonstrated that the inclusion of a placebo group is essential for valid assessment of the efficacy of antidepressant drugs. Although all groups improved on depression ratings in relation to their own baselines, only one group achieved a level of improvement that was significantly better than that of the placebo group.
No takes yet. Share an insight, caveat, or question.
Malitz et al. (1971) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: