Background

Dickersin and Min define publication bias as the failure to publish the results of a study ‘on the basis of the direction or strength of the study findings’.1 This non-publication introduces a bias which impacts the ability to accurately synthesise and describe the evidence in a given area.2 Publication bias is a type of reporting bias and closely related to dissemination bias, although dissemination bias generally applies to all forms of results dissemination, not simply journal publications. A variety of distinct biases are often grouped into the overall definition of publication bias.3 4

There are a number of risk factors and causes for publication bias identified in the literature.5 Research has shown causes of publication bias ranging from trialist motivation, past experience, and competing commitments; perceived or real lack of interest in results from editors, reviewers, or other colleagues; or conflicts of interest that would lead to the suppression of results not aligned with a specific agenda.3 6–9 The role of journal editors is particularly complex as the gatekeepers to publication. Significant results are more widely cited in medicine aligning the incentives of both investigators and editors towards these studies.10 A review by Song and colleagues reports studies showing that strength and …