Publication bias refers to a phenomenon in scientific reporting whereby authors are more likely to submit and journal editors are more likely to publish studies with “positive” results (i.e. results showing a significant finding) than studies with “negative” (i.e. supporting the null hypothesis) or unsupportive results. Due to such a bias, important—albeit negative—results (e.g., a study showing that a new treatment is ineffective) may never reach the larger scientific community.

1. Publication and reporting
biases and how they impact
publication of research

2. In a desert prison, an older prisoner befriends a new arrival. The young
prisoner talks constantly about escape, spinning plan after plan. After a few
months, he makes a break. He’s gone a week; then the guards drag him
back. He’s half-dead, crazy with hunger and thirst. He wails how awful it was
to the old prisoner: endless stretches of sand, no oasis, failure at every
turn. The old
prisoner listens for while, then says, “Yep.
I know. I tried those escape plans myself,
20 years ago.” The young prisoner says,
“You did? Why didn’t you tell me?”
The old prisoner shrugs”
“So who publishes negative results?”
“
”
Publication and reporting biases and how
they impact publication of research

3. What is publication bias?
Publication bias refers to a phenomenon in scientific reporting
whereby authors are more likely to submit and journal editors are
more likely to publish studies with “positive” results (i.e. results
showing a significant finding) than studies with “negative” (i.e.
supporting the null hypothesis) or unsupportive results.2
Due to such a bias, important—albeit negative—results
(e.g., a study showing that a new treatment is ineffective)
may never reach the larger scientific community.3
Publication and reporting biases and how
they impact publication of research

4. This bias toward publishing studies with positive results is just one
of the many different types of publication-related biases. As these
biases influence publication decisions, it is important that you
understand:
• What causes these biases
• The different types of biases, how they impact publication
decisions, and how to address them
• The need to counter publication and reporting biases
Publication and reporting biases and how
they impact publication of research

5. Causes of bias
Reporting and publication biases are caused by many different factors. Some of the main
causes are:
Many studies remain unpublished because researchers do not submit their work for
publication, thinking that journals will reject their papers because they do not have
positive or significant results to report. This submission-related bias has been termed
the file drawer problem.4
Journals may be biased toward positive results because negative results are less likely
to be cited and can thus lower a journal’s impact factor.
Study sponsors or funding sources may be biased towards results that favour their
interests. They may withhold the publication of unfavourable results and industry-
funded studies have led to positive results far more often than studies that are funded
or conducted by independent agencies.5,6
Publication and reporting biases and how
they impact publication of research

6. Different biases and how you can address them
The table in the next few slides lists different types of
publication and reporting biases existing in scientific
literature.1,7-11
It also offers some suggestions for addressing the different
types of biases. It is best to address these biases directly,
possibly while discussing the importance of the study in
your cover letter to the journal editor.
Publication and reporting biases and how
they impact publication of research

7. Type of bias What it means How to address this bias
Publication
bias
Studies with positive results
are more likely to be accepted
for publication than studies
with negative results.
Describe the specific problem that your study results will
help address. Point out that your negative results could
help counter publication bias12 (in fact, there are now
journals that exclusively publish negative results13) and
specify the outcome or views that your study can
potentially change.
Time lag bias Studies with positive findings
are likely to be published faster
than studies with negative
findings.
State why you think your study should be published
without delay (e.g., because the results could warrant
suspension of further trials or could affect how things
are being done in practice).
Multiple
publication
bias
Multiple publications are more
likely to be generated from a
single set of positive or
supportive results than from a
set of negative or unsupportive
results
If you have published a paper discussing a set of positive
results, do not publish another paper using the same set
of results (unless you are offering a radically different
perspective or analysis; always cross-reference the first
publication).
Publication and reporting biases and how
they impact publication of research

8. Type of bias What it means How to address this bias
Location bias Studies that report positive
results have a greater chance
of being published in widely
circulated, high-impact journals
than do studies with negative
results.
1. Don’t hesitate to submit your paper to a journal
with a high IF. Researchers have found that one of
the main reasons for this bias is that authors send
negative results to low-impact factor journals, and
not necessarily because journals are more likely to
reject these studies.14,15
2. When submitting to a high IF journal, explain how
the paper fits the journal’s scope and target
audience, why the negative results are important,
how the results challenge existing knowledge, and
why it is important that your research reaches a
wide audience.
Citation bias Researchers are more likely to
cite positive study results than
negative study results.
If you come across negative results related to your study,
be sure to mention them in your paper. Do not cite
studies that only support your own results, as this could
lead peer reviewers to suspect bias.
Publication and reporting biases and how
they impact publication of research

9. Type of bias What it means How to address this bias
Language
bias
The language in which a study
is published depends on
whether the study has positive
or negative results; studies
with positive results are more
likely to be published in
English-language journals.
Describe how your study results are of relevance to a
global audience and hence should be published in an
international journal that reaches out to this audience.
Outcome
reporting
bias
Researchers working on a study
in which multiple outcomes
were measured are more likely
to report positive outcomes
than negative outcomes.
Report any outcome that is relevant to your study,
whether it is positive or negative.
Publication and reporting biases and how
they impact publication of research

10. Publication and reporting biases and how
they impact publication of research
Type of bias What it means How to address this bias
Confirmatory
bias
Findings that conform to a
person’s (e.g., peer reviewer’s
or journal editor’s) beliefs and
hypotheses are more likely to
be recommended for
publication or published.
Relate your study to a previous study published in the
journal. Explain that your study results may go against
previously/widely held beliefs. Emphasize how your
study results can address an issue or change existing
perspectives.
Funding bias Study conclusions are biased in
favor of the sponsors’
products; findings that go
against the interests of study
sponsors never make it into
print.
Ensure that your sponsors do not influence your study
decisions—you should have access to all study data,
should analyze the data and choose the study
methodology independently, and should have the final
say in preparation and submission of the
manuscript.16Always disclose funding sources and any
conflict of interest. Manuscripts disclosing any funding
source are more likely to be published than those
without such a disclosure.11

11. Why you should proactively counter biases
Defend the purpose of research: By emphasizing the publication of positive results, these
biases have built “a systematically unrepresentative” body of literature17 and have “led to
scientific integrity being compromised.”18
Avoid adverse consequences: This trend can harm the public such as ineffective or
dangerous treatments, prolonged suffering among patients, and wasted resources (See
box: “Effects of publication bias”).
Maintain the integrity of scientific literature: By submitting methodologically sound
studies that have not yielded the expected results, highlighting the need to publish both
negative and positive results, conducting peer reviews objectively and without prejudice,
refusing to allow funding agencies influence study methodology, and reporting of
outcomes or publication decisions, you can act as gatekeepers of science.
A collective effort will ensure that published findings are more representative of all the
completed studies and can help maintain the integrity of scientific literature.
Publication and reporting biases and how
they impact publication of research

12. Effects of publication bias
Effects of publication bias on literature Effects of publication bias on public health
• Positive study findings may
dominate published literature.17
• Since fewer negative results are
published, there could be an
overestimation of the efficacy of
new treatments, social policies, or
new devices, and an
underestimation of their risks or
drawbacks.3,11,19
• Studies that find a treatment to be
harmful may never be published.7
• In 1980, researchers who found an increased
death rate among heart patients treated with a
class 1 anti-arrhythmic did not publish their study,
considering this result to be a chance finding.
Later, these drugs were found to actually lead to
increased mortality in heart patients. In 1993, the
researchers acknowledged that this non-
publication “was a good example of ‘publication
bias’”; 20 they admitted that had they reported
their findings 13 years earlier, they could have
saved lives.7,20
• A review of experimental studies examining the
adverse effects of cell phone use on health
revealed that industry-funded studies were least
likely to report a positive result.21
Publication and reporting biases and how
they impact publication of research

13. REFERENCES:
1. Sterne JAC, Egger M, Moher D. (Editors) (2008). Chapter 10: Addressing reporting biases in Cochrane Handbook for Systematic
Reviews of Interventions (eds. JPT Higgins and S Green). Version 5.0.1 [updated September 2008]. The Cochrane Collaboration.
2. Dickersin K (1990). The existence of publication bias and risk factors for its occurrence. Journal of the American Medical
Association, 263: 1385–1389.
3. McGauran N, et al. (2010). Reporting bias in medical research—a narrative review. Trials, 11: 37.
4. Rosenthal R (1979). The "file drawer problem" and tolerance for null results. Psychological Bulletin, 86(3): 638–641. doi:
10.1037/0033-2909.86.3.638.
5. Bodenheimer T (2000). Uneasy alliance—clinical investigators and the pharmaceutical industry. New England Journal of Medicine,
342: 1539–1544.
6. Bekelman JE, Li Y, Gross CP (2003). Scope and impact of financial conflicts of interest in biomedical research. Journal of the
American Medical Association, 289(4): 454–465.
7. Song F, Parekh S, Hooper L, Loke YK, Ryder J, Sutton AJ, et al (2010). Dissemination and publication of research findings: An
updated review of related biases. Health Technology Assessment, 14(8): iii,ix–xi.
8. Mahoney MJ (1977). Publication prejudices: An experimental study of confirmatory bias in the peer review system. Cognitive
Therapy and Research, 1(2): 161–175. doi: 10.1007/BF01173636.
9. Chopra SS (2003). Industry funding of clinical trials: Benefit or bias? Journal of the American Medical Association, 290(1): 113–
114.
10. Lesser LI, Ebbeling CB, Goozner M, Wypij D, Ludwig DS (2007). Relationship between funding source and conclusion among
nutrition-related scientific articles. PLoS Medicine, 4(1): e5.
11. Lee KP, Boyd EA, Holroyd-Leduc JM, Bacchetti P, Bero LA (2006). Predictors of publication: Characteristics of submitted
manuscripts associated with acceptance at major biomedical journals. Medical Journal of Australia, 184: 621–626.
Publication and reporting biases and how
they impact publication of research

14. REFERENCES:
12. Sridharan L & Greenland P (2009). Editorial policies and publication bias: The importance of negative studies (editorial
commentary) . Archives of Internal Medicine, 169: 1022–1023.
13. Kotze JD, Johnson CA, O’Hara RB, Vepsäläinen K, Fowler MS (2004). Editorial. Journal of Negative Results—Ecology & Evolutionary
Biology, 1: 1–5.
14. Koricheva J (2003). Non-significant results in ecology: A burden or a blessing in disguise? Oikos, 102: 397–401.
15. Leimu R & Koricheva J (2004). Cumulative meta-analysis: A new tool for detection of temporal trends and publication bias in
ecology. Proceedings of the Royal Society of London, B271: 1961–1966.
16. International Committee of Medical Journal Editors. Uniform requirements for manuscripts submitted to biomedical journals:
Writing and editing for biomedical publication [Accessed: June 14, 2011] Available from: http://www.ICMJE.org.
17. Rothstein HR, Sutton AJ, Borenstein M. (Editors) (2005). Chapter 1: Publication Bias in Meta-Analysis in Publication Bias in Meta-
Analysis: Prevention, Assessment and Adjustments (eds. HR Rothstein, AJ Sutton, and M Borenstein). John Wiley & Sons Ltd.:
Chichester, UK.
18. Editorial. The whole truth. New Scientist. May 1, 2004. Magazine issue 2445.
19. Scholey JM & Harrison JE (2003). Publication bias: Raising awareness of a potential problem in dental research. British Dental
Journal, 194: 235–237.
20. Editorial: Dealing with biased reporting of the available evidence. The James Lind Library. [Accessed: June 14, 2011] Available
from: www.jameslindlibrary.org.
21. Huss A, Egger M, Hug K, Huwiler-Müntener K, Röösli M (2007). Source of funding and results of studies of health effects of mobile
phone use: Systematic review of experimental studies. Environmental Health Perspectives, 115: 1–4.
Publication and reporting biases and how
they impact publication of research

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