What You See Depends on Where You're Looking and How You Look at It Publication Bias and Outcome Reporting Bias

Study publication bias is the decision to publish or not publish a study based on its results. Compared to unpublished work, published studies are more likely to have positive or statistically significant findings. Outcome reporting bias is opting to publish only a subset of the original variables recorded for a study, such that the inclusion of the variables in the published work is selectively based on the results. Statistically significant results have a higher likelihood of being fully reported compared to nonsignificant results, and a significant proportion of published articles describe outcome variables or data analyses that differ from the pre-specified trial protocol as originally conceived. Recognition that publication bias and outcome reporting bias contribute to a distorted perception of drug effects-inflated estimates of efficacy and underreporting of adverse events-has led to the development and expansion of publicly accessible databases that contain transparent information about clinical trials and their results.