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Placebo run-in period in studies of depressive disorders. Clinical, heuristic and research implications
F M Quitkin1, P J McGrath, J W Stewart
1Department of Therapeutics, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institution, USA.
Background:
In spite of the virtually ubiquitous nature of the initial 10-day placebo run-in period (IPR) in drug trials, there is little empirical data establishing its relevance.
Method:
Data from 593 subjects were examined retrospectively to determine whether or not the prognosis of subjects minimally improved during the IPR was different to those who were unimproved. The IPR period was single-blind and was followed by a six-week double-blind phase in all studies.
Results:
Twenty-six per cent of the subjects were minimally improved and 74% were unimproved. Approximately 10% of the subjects who were much improved were not followed systematically. Across a range of diagnosis, severity and chronicity subjects minimally improved (versus unimproved) after IPR had a more favourable prognosis whether assigned to drug or placebo.
Conclusions:
Change during IPR appears to be a meaningful predictor. Stratification should be considered in future antidepressant studies.