Publication Bias in Clinical Trials

December 20, 2010

An editorial1 in BMJexposes the problem of suppressed information from clinical trials performed on drugs and medical devices. Specifically, the authors discuss the effect of publication bias on systematic reviews in general, and on conclusions regarding the harms and benefits of treatments. The editorial calls for increased efforts to help reinstate trust in the scientific evidence used to maintain or improve patient care.


Manal Awad, BDS, MSc, PhD, is associate professor and head of the department of general and specialist dental practice at the University of Sharjah in Sharjah, UAE. JCDA sought the insights of Dr. Awad when the BMJ editorial was published.


JCDA Commentary

Evidence-based dental practice requires that practitioners search for the best available evidence and integrate this evidence to deliver the most suitable and efficient treatment option for their patients. The BMJ editorial1 helps keep practitioners aware of some of the uncertainties and controversies that surround the available scientific evidence—specifically the issue of publication bias.

One form of publication bias can occur when research studies that yield significant results in an expected direction are published, while studies that either show negligible results or results in an unexpected direction are not reported.2 Several factors can contribute to this phenomenon, including researchers who are not interested in authoring papers that don't show anticipated results. In addition, journal editors and peer reviewers may be reluctant to publish or provide positive feedback respectively on research that does not show expected results.

More worrisome, publication bias can sometimes be driven by those who have funded the research in the first place. For example, if a research study is financed by a private pharmaceutical company, it might favour a particular new treatment over the standard of care.2 A more subtle form of publication bias can occur when researchers are selective regarding the outcomes they choose to report, irrespective of the original trial plan.3

Regardless of the reasons, the main concern to dental practitioners is whether publication bias will affect our clinical decision-making and possibly result in patient harm. The editorial calls for more efforts to help reduce the impact of publication bias by having leading biomedical journals encourage reviewers to give careful consideration to studies that may have important negative results. Making sure that all results from clinical trials are accessible would effectively prevent the concealment of some study findings.


  1. Loder E, Godlee F. Missing clinical trial data: setting the record straight. BMJ. 2010;341:c5641.
  2. Crawford JM, Briggs CL, Engeland CG. Publication bias and its implication for evidence-based decision making. J Dent Educ. 2010;74(6):593-600.
  3. Moreno SG, Sutton AJ, Turner EH, Abrams KR, Cooper NJ, Palmer TM et al. Novel methods to deal with publication biases: secondary analysis of antidepressant trials in the FDA trial registry database and related journal publications. BMJ. 2009;339:b2981.