Role of clinicians’ outcome expectations for treatment response in depression - is blinding at time of assessment necessary to control rater bias?

• Applicants: Privatdozentin Dr. Gertraud Gradl-Dietsch; Dr. Marcel Wilhelm
• Subject Area: Clinical Psychiatry, Psychotherapy, Child and Adolescent Psychiatry ; Personality Psychology, Clinical and Medical Psychology, Methodology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 553393816

Discrepancies between self- and clinician-rated outcomes in the efficacy of antidepressant treatment among children, adolescents, and adults have been a longstanding concern. Clinician ratings consistently yield higher effect sizes than self-ratings in randomized controlled trials (RCTs) for major depressive disorder (MDD). This study aims to test the hypothesis that clinician expectancy at the end of treatment phases contributes to these discrepancies. A cost-efficient experimental design will be used, involving clinical personnel experienced in treating adult or adolescent patients with mental disorders. Participants will evaluate two videos depicting 20-minute clinical assessments of female actors portraying moderately depressed patients. These core videos will be preceded by a five-minute trailer providing contextual framing related to either a baseline assessment or an end-of-study assessment. One video shows a patient from an antidepressant RCT and the other shows a patient from a psychotherapy RCT. Ratings will be performed using the Hamilton Depression Scale-17 (HAMD-17), a widely recognized tool in pharmacological RCTs for depression. The primary hypothesis posits that depression scores will be higher for videos framed as baseline assessments compared to those framed as end-of-treatment assessments. The study will be conducted at two sites (Essen, Marburg) for enhanced generalizability. Eight videos will be produced, each consisting of a core video and a framing trailer. Besides the different treatment forms, two age groups (late adolescence, middle age) will be represented. A total of 358 raters, comprising both male and female physicians and psychologists, will be recruited from psychiatric hospitals and psychotherapy training programs. These raters will be randomized to view one of the videos and provide their clinical ratings. The primary analysis will assess the difference in depression scores based on the framing trailer. Secondary analyses will explore the differences between psychotherapy and pharmacotherapy as well as potential moderators, including the age group of the patient, the rater's experience, and their beliefs about the efficacy of pharmacological and psychological treatments. Additional exploratory comparisons will assess potential effects of rater demographics and professional background. This study addresses a critical gap in understanding potential biases influencing clinician ratings in RCTs. By isolating the effect of clinician expectancy, the findings will provide valuable insights into the interpretation of RCT results and influence future trial designs. Using a novel video-based experimental design, this study aims to shed light on the potential influence of clinician expectancy on depression ratings. The findings will have significant implications for the design and interpretation of RCTs in MDD and other conditions using clinician-rated outcomes.

• DFG Programme: Research Grants