Chronic Publication Bias Found in Clinical Studies


Systematic reviews of the published medical literature may often be unreliable due to chronic publication bias, according to a study in PLOS One.

A team of German, Swiss and American researchers compiled a list of studies that had been approved by research ethics committees (RECs) or included in trial registries, and sought to determine what percentage of these had been subsequently published, and what if any patterns were detectable in whether they’d been published.

“Overall, only about half of clinical and preclinical studies approved by RECs or included in trial registries are published as full journal articles,” the researchers wrote. “We also found evidence for dissemination bias in that studies with statistically significant results were more likely to be published than those without.”

(Full text) (Schmucker, Christine et al. Extent of Non-Publication in Cohorts of Studies Approved by Research Ethics Committees or Included in Trial Registries. PLOS One. December 23, 2014. DOI: 10.1371/journal.pone.0114023)


  1. The importance of this work and its implications for all of medical therapeutics can not be overstated. From the article:
    “When results are not published or are published selectively based on the direction or the strength of the findings, healthcare professionals and consumers of healthcare cannot base their decisions on the full body of current evidence. This ignorance can lead to the use of ineffective or harmful interventions and to waste of scarce health-care resources. For example, when unpublished studies were included in a meta-analysis, the antidepressant reboxetine was shown to have more adverse effects but no better efficacy than placebo for treatment of major depression – a different finding from that when only published studies were included. [60]”

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    • Yeah, The problem is that journals often don’t want to publish negative results which not only leads to them not being published but also makes the researchers more likely to manipulate results in order to get things out in a “publish or perish” culture. Science had been riddled with wrong incentives lately.

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