Depression trial results: A cross-sectional study of ClinicalTrials.gov.

Published clinical trials represent a subsample of the objective information needed to appraise treatments for depression. We characterize the extent of selective and delayed reporting in a systematic review (PROSPERO #CRD42020173606) of depression trial results registered on ClinicalTrials.gov. Inclusion criteria were studies registered on ClinicalTrials.gov with depression as the condition, had enrolled ages 18 and over, were completed between January 1, 2008 and May 1, 2019, and had posted results by February 1, 2022. Cox regression analyses of time to result posting from registration and from study completion included enrollment as a covariate. Among 442 protocols, median result posting occurred over two years after study completion and five years after registration. Among protocols with incomplete results, effect sizes (d or W) were calculated for 134 protocols. Median effect sizes for protocols with incomplete results were small (0.16, 95% CI 0.08, 0.21). For 28% of protocols, observed effects were contrary to the expected direction. Between-group effect size calculations were based on post-treatment data as pre-treatment data were inconsistently provided. Although drug and device trials in the U.S. are required to register on ClinicalTrials.gov, compliance is imperfect, and submissions are not peer reviewed. For depression treatment trials, long intervals between study completion and posting of results are common. Further, investigators often fail to report the results of statistical tests. Failure to post trial results in a timely manner and omission of statistical test reporting may lead to overestimates of treatment effects in systematic literature reviews.