It is notoriously difficult to fully blind clinical trials of psychological interventions. At most, psychotherapy trials are said to be single blinded, because study participants typically know what group they have been allocated to and therapists know the treatments they deliver. It is somewhat easier to ensure that the study investigators, outcome assessors, and other study personnel remain blinded to treatment allocation. A review of psychotherapy trial reports1 published in 6 top psychiatry journals in 2017 and 2018 revealed that only 59% of the included trials reported adequate blinding of outcome assessors. Participants, therapists, data managers, data safety and monitoring committees, statisticians, and those making conclusions were typically either not blinded, or it was unclear whether blinding was performed.1 Many psychotherapy trials are not blinded at all and rely on participant self-reports as their primary outcome measures. This inevitably results in lower-quality scores in meta-analyses using risk of bias tools.2 Thus, it is clear that more needs to be done to improve the planning of blinding procedures (and their reporting) in psychotherapy trials. The simple message is that all study personnel and participants who can potentially be blinded should be blinded (Table).
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Mataix-Cols D, Andersson E. Ten Practical Recommendations for Improving Blinding Integrity and Reporting in Psychotherapy Trials. JAMA Psychiatry. 2021;78(9):943–944. doi:10.1001/jamapsychiatry.2021.1419
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