Publication bias in clinical trials due to statistical significance or direction of trial results

EDITORIAL NOTE: There is a more recent Cochrane review on this topic: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.MR000011.pub3/full. BACKGROUND: The tendency for authors to submit, and of journals to accept, manuscripts for publication based on the direction or strength of the study findings has been termed publication bias. OBJECTIVES: To assess the extent to which publication of a cohort of clinical trials is influenced by the statistical significance, perceived importance, or direction of their results. SEARCH STRATEGY: We searched the Cochrane Methodology Register (The Cochrane Library Online Issue 2, 2007), MEDLINE (1950 to March Week 2 2007), EMBASE (1980 to Week 11 2007) and Ovid MEDLINE In-Process 95% confidence interval 2.68 to 5.68). This corresponds to a risk ratio of 1.78 (95% CI 1.58 to 1.95), assuming that 41% of negative trials are published (the median among the included studies, range = 11% to 85%). In absolute terms, this means that if 41% of negative trials are published, we would expect that 73% of positive trials would be published.Two studies assessed time to publication and showed that trials with positive findings tended to be published after four to five years compared to those with negative findings, which were published after six to eight years. Three studies found no statistically significant association between sample size and publication. One study found no significant association between either funding mechanism, investigator rank, or sex and publication. AUTHORS' CONCLUSIONS: Trials with positive findings are published more often, and more quickly, than trials with negative findings.