Placebo-controlled randomized clinical trials of antidepressants for major depressive disorder: Analysis of ClinicalTrials.gov, 2008-2022

The purpose of this study was to analyze the key aspects of the design of contemporary placebo -controlled randomized clinical trials (RCTs) of antidepressants enrolling patients with major depressive disorder (MDD) aged 18 years or older, especially the outcome measures and the eligibility criteria. The study included 122 RCTs registered with ClinicalTrials.gov and started from 2008 through 2022. Most RCTs assessed only clinical remission, with proportion of trials with outcome measures related to functional remission being rather low (n = 34; 28 %). Clinical remission was mostly evaluated in acute phase of depression, and only 7 (6 %) trials assessed the prevention of relapse. Proportion of trials utilizing self -report questionnaires that provide important information complementary to clinician -rated scales was moderate (n = 66; 54 %). Another problem in included RCTs was common use of stringent eligibility criteria. For instance, minimal symtpom severity required for the patient's inclusion was listed in 104 RCTs (85 %), and 41 RCTs (34 %) excluded patients based on comorbid anxiety disorders. Most RCTs (n = 103; 84 %) excluded older patients, and only 6 (5 %) trials were dedicated exclusively to them. To ensure optimal development of clinical pharmacotherapy of MDD, the investigators should consider modification of some of the key aspects of the design of RCTs of antidepressants.