title: Accounting for perception, placebo and unmasking effects in estimating treatment effects in randomised clinical trials.
abstract: There is a rich literature on the role of placebos in experimental design and evaluation of therapeutic agents or interventions. The importance of masking participants, investigators and evaluators to treatment assignment (treatment or placebo) has long been stressed as a key feature of a successful trial design. Nevertheless, there is considerable variability in the technical definition of the placebo effect and the impact of treatment assignments being unmasked. We suggest a formal concept of a 'perception effect' and define unmasking and placebo effects in the context of randomised trials. We employ modern tools from causal inference to derive semi-parametric estimators of such effects. The methods are illustrated on a motivating example from a recent pain trial where the occurrence of treatment-related side effects acts as a proxy for unmasking.
authors: Division of Biostatistics, School of Public Health, University of California, Berkeley, CA, USA.
authors: Farid
authors: F
authors: Jamshidian
authors: Division of Biostatistics, School of Public Health, University of California, Berkeley, CA, USA.
authors: Alan E
authors: AE
authors: Hubbard
authors: Division of Biostatistics, School of Public Health, University of California, Berkeley, CA, USA jewell@berkeley.edu.
authors: Nicholas P
authors: NP
authors: Jewell
mesh_terms: D000588:Amines / Q000627:therapeutic use; D003509:Cyclohexanecarboxylic Acids / Q000627:therapeutic use; D005260:Female; D000077206:Gabapentin; D006801:Humans; D008297:Male; D010146:Pain / Q000188:drug therapy; D015990:Placebo Effect; D010919:Placebos; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D012107:Research Design; D005680:gamma-Aminobutyric Acid / Q000627:therapeutic use
chemical_list: D000588:Amines; D003509:Cyclohexanecarboxylic Acids; D010919:Placebos; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin