Biases Specific To Systematic Reviews

Question 1

Publication bias.

Answer 1

Studies researching unpopular research topics or treatments don’t get published, so their evidence is unavailable to reviewers.

Question 2

Time lag bias.

Answer 2

Delays in publication prevent the research from being found by practitioners or reviewers in time for their review.

Question 3

Duplicated publication bias.

Answer 3

The same results from the same studies are repeatedly published, suggesting that there is more evidence than their actually is.

Question 4

Outcome reporting bias.

Answer 4

Mainly desirable or expected results or statistically significant results get published, even though other results are equally valid and informative.

Question 5

Citation bias.

Answer 5

If a study is cited a lot by many other authors, reviewers are more likely to find that research compared with studies that are rarely cited, or not cited at all.

Question 6

Database inclusion bias.

Answer 6

Studies are much more easily found if they are available from online databases.

Question 7

Language bias.

Answer 7

A preference among reviewers for studies published in the language they understand, commonly, but not always English.

Question 8

Reviewers personal bias.

Answer 8

Reviewers may unfairly exclude an article because they don’t like the topic or the results, even though the results are valid and relevant.