PubMed is a free database provided by the US government. It primarily consists of MEDLINE, a database of over 30 million citations from the biomedical literature.
If you've searched MEDLINE on other platforms (like EBSCO or OVID), the difference in content is that PubMed also includes PubMed Central, an archive of full-text journal articles; and the Bookshelf, an archive of books, reports, and other materials. In terms of searching, the technical syntax in PubMed is very different from what you would use in those other platforms, even though the controlled vocabulary is the same.
PubMed's default search uses Automatic Term Mapping (ATM) to make an educated guess as to what you're looking for. The most important thing ATM checks for is whether there is a good match for the words or phrases in your search within PubMed's controlled vocabulary (MeSH, or Medical Subject Headings).
ATM is fine, but in a systematic search, you'll want to have more control of what PubMed is doing. That means:
Controlled vocabulary is the specialized language used by a database to describe the citations within it. The controlled vocabulary used in PubMed is called MeSH, or Medical Subject Headings. Below is a video about two ways to locate relevant MeSH headings and use them to further develop your concept table.
This video shows how to build a search strategy in PubMed using the keywords and controlled vocabulary from your concept table, AND and OR, and PubMed's unique search syntax.
PubMed is a database, which means each citation is a record made up of many different fields. Some examples of fields include title, abstract, and MeSH. Search tags allow you to tell PubMed where in the record to search. As you construct your search, you'll be looking in a few specific fields:
Searches only the MeSH field.
Searches only in MeSH, and explicitly excludes the narrower terms underneath your search term in the hierarchy.
Searches in title, abstract, and keywords (also collection title and other abstract, but those are less relevant for article searching).
[tiab] is the best choice, in most cases, for searching keywords from your concept table. You should also use it to search your MeSH terms as keywords, just in case!
This searches in lots of different fields, including title, abstract, MeSH, MeSH Subheadings, Publication Types, Substance Names, various author name fields, and more.
Because [tw] includes the MeSH field, it has a tendency to duplicate your MeSH search. It may also be too sensitive, returning lots of irrelevant results. As a result, I recommend using [tiab] instead, in most circumstances. There may be cases in which [tw] is appropriate, but we can work that out together.
Essential things to know about truncation in PubMed:
You can truncate a phrase, but only the last word in the phrase. To do this:
Phrase searching works differently in PubMed than in most databases, so see the next box on this page to learn more about it.
There are some useful examples of truncation in the Develop & Document Your Search Strategy tab, so don't hesitate to look back at those as you plan you search!
Phrase searching in PubMed is a little tricky! There are three different ways to do it:
Put "double quotes" around your phrase: "cardiovascular exercise"
PubMed first checks to see if it’s indexed this as a common phrase in [All Fields]. If it is indexed there, so PubMed executes the search as requested. If it doesn’t show up in the phrase index, PubMed ignores the quotation marks and tries to match the words x AND y using ATM.
Use a [search tag]: cardiovascular exercise [tiab]
PubMed behaves exactly as in Option 1.
Use a hyphen: cardiovascular-exercise
PubMed first checks to see if it’s indexed this as a common phrase in the broadest field (All Fields). If it isn't there, PubMed returns no results for your phrase.
Sometimes you'll notice you're getting a lot of results on animal research that are making it hard to find the relevant human research studies. Because humans are technically animals, asking PubMed to limit to human research is harder than you might expect.
This hedge is designed for identifying research on humans.
To use this hedge:
In the image below, imagine that #1 refers to your optimal set of search results.
Full text of the hedge to use in your search:
NOT ("animals"[MeSH Terms] NOT "humans"[MeSH Terms])
Search filters, or hedges, are designed to narrow the scope of searches based on specific criteria. For instance, the PubMed human research hedge above excludes search results that are tagged with MeSH indicating they are only about animal research. Other hedges focus on things like study types or age groups. Filters are customized based on database and platform (such as Medline via PubMed vs. Medline via Ovid). Some attempt to maximize precision (so you don't have to screen as many potentially irrelevant results) while others aim to maximize sensitivity or recall (reducing the number of relevant sources you miss).
It's important to remember that all search filters are a compromise: the more restrictions you put on a search, the more likely you are to inadvertently exclude something useful. Some hedges are validated, while others aren't. You'll need to use your own judgment when applying filters to your searches. Be sure to cite them in your methods, and document if you made any modifications (which, even for a validated hedge, means the validity is now in question).
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