Blind man's bluff: effectiveness and significance of psychotherapy and pharmacotherapy blinding procedures in a clinical trial

Abstract

No study has reported on the comparative effectiveness of blinding procedures for psychotherapy and pharmacotherapy conditions in treatment efficacy studies or the potential impact of failure to maintain a psychotherapy blind. In a randomized clinical trial, we found, from the perspective of clinical evaluators who were unaware of the patient's treatment assignment, procedures intended to protect the psychotherapy blind were only modestly effective but comparable to standard procedures used to maintain pharmacotherapy blinds. Second, accuracy of guessing each form of treatment (psychotherapy or pharmacotherapy) was not independent of the other. Third, findings suggested the importance of maintaining both psychotherapy and pharmacotherapy blinds, as subjective ratings of treatment outcome were significantly different depending on whether the clinical evaluator had correctly guessed the patients' true treatment condition.