Systematic Review of Blinding Assessment in Randomized Controlled Trials in Schizophrenia and Affective Disorders 2000-2010

Abstract

Background: Blinding is an integral part of many randomized controlled trials (RCTs). However, both blinding and blinding assessment seem to be rarely documented in trial reports. Method: Systematic review of articles on RCTs in schizophrenia and affective disorders research during 2000-2010. Results: Among 2,467 publications, 61 (2.5%; 95% confidence interval: 1.9-3.1%) reported assessing participant, rater, or clinician blinding: 5/672 reports on schizophrenia (0.7%; 0.3-1.6%) and 33/1,079 (3.1%; 2.1-4.2%) on affective disorders, without significant trends across the decade. Rarely was blinding assessed at the beginning, in most studies assessment was at the end. Proportion of patients' and raters' correct guesses of study arm averaged 54.4 and 62.0% per study, with slightly more correct guesses in treatment arms than in placebo arms. Three fourths of responders correctly guessed that they received the active agent. Blinding assessment was more frequently reported in papers on psychotherapy and brain stimulation than on drug trials (5.1%, 1.7-11.9%, vs. 8.3%, 4.3-14.4%, vs. 2.1%, 1.5-2.8%). Lack of assessment of blinding was associated with: (a) positive findings, (b) full industrial sponsorship, and (c) diagnosis of schizophrenia. There was a moderate association of treatment success and blinding status of both trial participants (r = 0.51, p = 0.002) and raters (r = 0.55, p = 0.067). Many RCT reports did not meet CONSORT standards regarding documentation of persons blinded (60%) or of efforts to match interventions (50%). Conclusions: Recent treatment trials in major psychiatric disorders rarely reported on or evaluated blinding. We recommend routine documentation of blinding strategies in reports.

Can Assessors in a Psychotherapy Trial Be Successfully Blinded? Analysis of a Randomized Controlled Trial on Psychotherapy for Refractory Insomnia in Residual Depression

“…The other factors led neither to correct nor to incorrect guessing. The agreement rate of the present study at 63.5% seems very similar to that described in the recent review at 62% [1]. The kappa value at 0.28 has led us to conclude that blinding was successful.…”

“…In psychiatry trials, there are several cases where blindness was not fully maintained [1]. Successful blinding in our study may be due to employing not pharmacotherapy but psychotherapy as the active intervention.…”

“…The recent systematic review of Baethge et al [1] focuses on the proportion of recent randomized controlled trials that present a method of blinding procedures in psychiatric disorders. They report that only 4 of 78 papers in psychotherapy trials do so.…”

Combining Antidepressants in Acute Treatment of Depression: A Meta-Analysis of 38 Studies Including 4511 Patients

“…Therefore, it is difficult to judge the quality of blinding-a problem that has been shown to be prevalent in psychiatric research. 44 In addition, some of the study arms (step 2 in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) Study [45][46][47] ) were not meant to be directly compared, and step 2 and step 4 of the STAR*D trial [45][46][47][48] were sequential treatments among the same study population. It is, therefore, reassuring that results were supported by the analysis of trials with low risk of bias.…”

Disagreement between Therapist Raters and Independent Evaluators in a Controlled Clinical Trial of Interpersonal Psychotherapy for Depressed Pregnant Women

“…Blinding, an integral part of many RCTs, is intended to limit bias by keeping both participants and investigators masked to the assigned intervention. 2 Several psychotherapy studies using controlled research designs have demonstrated treatment efficacy in clearly delineated populations. 3,4 Psychotherapy efficacy studies use RCT designs to compare the application of manualized psychotherapies delivered over a fixed number of sessions to treat individuals diagnosed with specific uncomplicated disorders.…”