Successful blinding is an important feature of double-blind randomized controlled trials, & ensures that the safety and efficacy of treatments are accurately appraised; but blinding is not successful among either patients or investigators

A systematic review and meta-analysis of the success of blinding in antidepressant RCTs. Amelia J Scott, Louise Sharpe, Ben Colagiuri. Psychiatry Research, November 24 2021, 114297. https://doi.org/10.1016/j.psychres.2021.114297

Highlights

• Successful blinding is an important feature of double-blind randomized controlled trials, and ensures that the safety and efficacy of treatments are accurately appraised.

• In a range of fields (e.g. chronic pain, general medicine), few trials report assessing the success of blinding.

• We do not know the frequency or success of blinding assessment among antidepressant RCTs within depression.

• Only 4.7% of RCTs examining antidepressants in depression assess blinding.

• Overall, blinding is not successful among either patients or investigators.

Abstract: Successful blinding in double-blind RCTs is crucial for minimizing bias, however studies rarely report information about blinding. Among RCTs for depression, the rates of testing and success of blinding is unknown. We conducted a systematic review and meta-analysis of the rates of testing, predictors, and success of blinding in RCTs of antidepressants for depression. Following systematic search, further information about blinding assessment was requested from corresponding authors of the included studies. We reported the frequency of blinding assessment across all RCTs, and conducted logistic regression analyses to assess predictors of blinding reporting. Participant and/or investigator guesses about treatment allocation were used to calculate Bang's Blinding Index (BI). The BI between RCT arms was compared using meta-analysis. Across the 295 included trials, only 4.7% of studies assessed blinding. Pharmaceutical company sponsorship predicted blinding assessment; unsponsored trials were more likely to assess blinding. Meta-analysis suggested that blinding was unsuccessful among participants and investigators. Results suggest that blinding is rarely assessed, and often fails, among RCTs of antidepressants. This is concerning considering controversy around the efficacy of antidepressant medication. Blinding should be routinely assessed and reported in RCTs of antidepressants, and trial outcomes should be considered in light of blinding success or failure.

Keywords: Randomized controlled trialsBlindingDepressionAntidepressants