Occurs when the publication of research depends on the direction of the study results and whether they are statistically significant.
Publication bias is the bias that can result in a systematic review because studies with statistically significant results are more likely to be published than those that show no effect (particularly for intervention studies). Publication bias can be minimized if an attempt is made to include in a systematic review all relevant published and unpublished studies. This process can be facilitated by international registers of trials.
Bias produced when the published studies do not represent adequately all the studies carried out on a specific topic. Many facts can origin this bias, although the best known is the trend to publish statistically significant (p < 0.05) or clinically relevant (high magnitude albeit non-significant) results. Other variables influencing publication bias are sample size (more in small studies), type of design (less in well conducted randomized controlled trials), funding, conflict of interest, prejudice against an observed association (for example, cocaine consumption and non-adverse effect on fetus), sponsorship.
The influence of study results on the chances of publication and the tendency of investigators, reviewers, and editors to submit or accept manuscripts for publication based on the direction or strength of the study findings. Publication bias has an impact on the interpretation of clinical trials and meta-analyses. Bias can be minimized by insistence by editors on high-quality research, thorough literature reviews, acknowledgement of conflicts of interest, modification of peer review practices, etc.