Blinding and bias in a hypnotic clinical trial

Area of Science:

• Clinical Psychology
• Psychopharmacology
• Clinical Trial Methodology

Background:

• Blinding is crucial in randomized clinical trials (RCTs) to prevent bias.
• Limited information exists on the frequency of unblinding in hypnotic RCTs.

Purpose of the Study:

• To assess the accuracy of treatment assignment "best guesses" by participants, coordinators, and physicians in a hypnotic RCT.
• To evaluate the effectiveness of blinding in the Reducing Suicidal Ideation Through Insomnia Treatment (REST-IT) study.

Main Methods:

• A double-blind, placebo-controlled RCT involving 103 adults with major depressive disorder, insomnia, and suicidal ideation.
• Participants, study coordinators, and physicians independently guessed the assigned treatment (zolpidem extended-release vs. placebo) post-study.
• Statistical analysis compared guessing accuracy against chance and assessed agreement between parties.

Main Results:

• Patient guesses were correct 58.4% of the time, coordinators 53.9%, and physicians 49.4%.
• None of these "best guesses" significantly differed from chance.
• Inter-rater agreement between patient/coordinator, patient/doctor, and coordinator/doctor dyads ranged from 75% to 78%.

Conclusions:

• The "best guesses" not differing from chance suggest the study's blind was maintained.
• Assessment bias was likely minimized in this RCT of zolpidem ER versus placebo.
• Findings may not generalize to other hypnotics or different RCT designs.