Systematic Reviews for the Health Sciences: Search Hedges

This page was created by Krystal Madkins, former practicum student at LHS Chicago.

What are search hedges?

Search hedges are pre-defined comprehensive combinations of search terms used to retrieve journal articles. They are most often used to retrieve articles by study type (e.g., systematic reviews) or research topic (e.g., HIV/AIDS). Hedges are typically created by librarians and composed of controlled vocabulary, such as MeSH (Medical Subject Headings), in databases like PubMed and CINAHL. Hedges save researchers time by allowing them to use pre-defined searches as often as needed rather than creating new searches each time. Hedges may also be validated for sensitivity, specificity, precision, and accuracy to ensure that the most optimal search results are returned. 

Why use search hedges?

In addition to saving researcher's time in building searches from scratch, search hedges may be beneficial when conducting systematic reviews in which comprehensive retrieval of articles is important or when narrowing the scope of searches - for example, narrowing to exclude animal research. 

Search hedges vs. search filters

Although search hedges and search filters are sometimes used interchangeably, the terms have different meanings. The person credited with creating the concept of a search hedge defines it as "groups of terms representing concepts which occur frequently in the search requests, but not always in the same way...[and] combine terms which are synonyms, variant spellings of the same term or terms that are related in some other way" (Campbell, 2016). In contrast, search filters are "designed to extract articles with specific characteristics" such as clinical concepts or static characteristics such as age groups. The PubMed Clinical Queries tool is an example of a search filter. 

For more information on search hedges and filters, read Campbell's brief commentary. 

Getting started with search hedges

Below are links to search hedges that can be copied into search bars of commonly used databases like PubMed, EMBASE, and PsycINFO.

Please Note:  Search hedges may also need to be modified to fit research needs. Not all search hedges can be used interchangeably across databases because of differences in controlled vocabulary and would need to be adapted in each database. Also, not all of the search hedges shared on this page have been validated. If you modify a validated hedge, it can no longer be considered validated.

Citation: Campbell, S. (2016). What is the difference between a filter and a hedge? Journal of the European Association for Health Information and Libraries, 12(1), 4-5.