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Placebo Run-In Periods in Randomized Clinical Trials of Antidepressants Not Effective
Although there are few proven benefits, placebo run-in (PRI) periods are common in randomized clinical trials (RCTs) for antidepressants, according to new research published in JAMA Psychiatry.
Researchers aimed to assess the association between the use of PRI periods to placebo and drug response, as well as drug-placebo difference, in RCTs for antidepressants.
“They aim to increase sensitivity to detect drug effects; however, the association of PRI periods with study outcomes remains unclear. This is concerning given the costs of PRI periods to patients and investigators,” wrote Amelia J Scott, PhD, School of Psychology, University of Sydney, Sydney, New South Wales, Australia, and co-researchers.
Through this systematic review and meta-analysis, researchers compiled a total of 347 double-blind, placebo controlled RCTs from data sources, including MEDLINE, PsycINFO, Embase, the Cochrane Central Register of Controlled Trials, and repositories of unpublished works leading up to July 2021 of antidepressant medication for adults. A total of 89,183 participants were included.
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Researchers looked for the primary depression symptom measure reported in each study to find the effect sizes of placebo response, drug response, and the difference between drug and placebo using random-effects meta-analysis.
When compared with studies that did not use PRI period, studies using PRI period had smaller placebo responses and smaller drug response size. There was no drug-placebo difference between studies using PRI period and studies not using PRI period, and no difference in the likelihood of response when comparing drug with placebo.
“This study suggests that RCTs using PRI periods yield smaller within-group changes across both placebo and drug groups compared with RCTs without PRI periods,” Dr Scott et al concluded. “…given the resources and probable deception required and risk to external validity, the practice of using PRI periods in RCTs of antidepressants should be ended.”
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