1. How do they add up? The interaction between the placebo and treatment effect: A systematic review
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Rémy Boussageon, Jeremy Howick, Raphael Baron, Florian Naudet, Bruno Falissard, Ghina Harika‐Germaneau, Issa Wassouf, François Gueyffier, Nemat Jaafari, Clara Blanchard, Jonchère, Laurent, Laboratoire de Biométrie et Biologie Evolutive - UMR 5558 (LBBE), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, Collège Universitaire de Médecine Générale [Lyon] (CUMG), Université de Lyon, Centre d'Investigation Clinique [Rennes] (CIC), Université de Rennes (UR)-Hôpital Pontchaillou-Institut National de la Santé et de la Recherche Médicale (INSERM), CHU Pontchaillou [Rennes], Centre de recherche en épidémiologie et santé des populations (CESP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpital Paul Brousse-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Paris-Saclay, Centre Hospitalier Henri Laborit (CHL), Centre hospitalier universitaire de Poitiers (CHU Poitiers), and No funding was received for this study by any of the co-authors.
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Pharmacology ,[SDV]Life Sciences [q-bio] ,Therapeutic alliance ,Evidence-based practice ,Placebo Effect ,Drug effect ,[SDV] Life Sciences [q-bio] ,Clinical trials ,[SDV.SP.PHARMA] Life Sciences [q-bio]/Pharmaceutical sciences/Pharmacology ,[SDV.SP.PHARMA]Life Sciences [q-bio]/Pharmaceutical sciences/Pharmacology ,Humans ,Pharmacology (medical) ,Treatment outcome ,Placebo - Abstract
International audience; AIM: The placebo effect and the specific effect are often thought to add up (additive model). Whether additivity holds can dramatically influence the external validity of a trial. This assumption of additivity was tested by Kleijnen et al. in 1994 but the data produced since then has not been synthetized. In this review, we aimed to systematically review the literature to determine whether additivity held. METHODS: We searched Medline and PsychInfo up to 10/01/2019. Studies using the balanced placebo design (BPD), testing two different strengths of placebos, were included. The presence of interaction was evaluated by comparing each group in BPD with analysis of variance or covariance. RESULTS: 30 studies were included and the overall risk of bias was high: four found evidence of additivity and 16 studies found evidence of interaction (seven had evidence of positive additivity). CONCLUSION: Evidence of additivity between placebo and specific features of treatments was rare in included studies. We suggest interventions for placebo-sensitive ailments should be tested in trials designed to take interactions seriously once an exploratory RCTs has proven their efficacy with sufficient internal validity.
- Published
- 2022
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