PubMed has some advanced searching features that can help narrow or broaden your searches and add specificity. Understanding these concepts will help you make complex, comprehensive searches. We will cover Automatic Term Mapping, Field tags, and Mesh terms on this page—three interconnected concepts that will help in understanding how you can utilize PubMed to the fullest.
When you enter a search into PubMed such as: (college OR higher education OR university) AND (health OR medicine), PubMed applies a process called Automatic Term Mapping (ATM), that takes your search and expands and changes it in different ways.
If you select the Advanced Search page, find the History section and expand the details field, you will see what PubMed actually searched. For the simple search above, it uses ATM to actually search this:
("college"[All Fields] OR "college s"[All Fields] OR "colleges"[All Fields] OR ("high educ dordr"[Journal] OR ("higher"[All Fields] AND "education"[All Fields]) OR "higher education"[All Fields]) OR ("universiti"[All Fields] OR "universities"[MeSH Terms] OR "universities"[All Fields] OR "university"[All Fields] OR "university s"[All Fields])) AND ("health"[MeSH Terms] OR "health"[All Fields] OR "health s"[All Fields] OR "healthful"[All Fields] OR "healthfulness"[All Fields] OR "healths"[All Fields] OR ("medicin"[All Fields] OR "medicinal"[All Fields] OR "medicinally"[All Fields] OR "medicinals"[All Fields] OR "medicine"[MeSH Terms] OR "medicine"[All Fields] OR "medicine s"[All Fields] OR "medicines"[All Fields]))
Automatic Term Mapping can be helpful, as it expands your search and looks for relevant keywords, but it can also lead to a less precise and relevant set of search results. Some solutions for turning off Automatic Term Mapping include putting your keywords in quotes or using a field tag. Field tags are explored below.
Field tags in PubMed help you indicate where you would like to search for a particular keyword. There are many places to search in PubMed, such as the title of an article, the abstract of an article, the author name or affiliation, etc. Each of these and more has a corresponding field tag, and you can read about them in the PubMed User Guide. You can add specificity to your search by showing exactly where you want PubMed to search. Field tags are shown in the search next to the keyword in brackets, for example: Keyword[Field tag].
Here are some common field tags. They each have a full version and an abbreviated version that work in the same way in the search:
Keyword[All Fields] / Keyword[all] - searches all available fields at the same time
Keyword[Title/Abstract] / Keyword[tiab] - searches only the title and abstract of articles. You can also search just the title [ti] or just the abstract [ab].
Keyword[Publication Type] / Keyword[pt] - the type of publication the article is listed as. Use the list in the PubMed User Guide to find different types of publications in PubMed
When you put in a simple keyword search as demonstrated in the section on Automatic Term Mapping, PubMed picks the field tag [All Fields] by default. It will also find Mesh terms corresponding to your keywords and search them in their own field tag. Mesh terms are described further in the Mesh section on this page.
Records for articles in PubMed get assigned Mesh terms.These Mesh terms are subject headings that are considered the most specific word or group of words that captures the essence of the subject. In PubMed, they are called Mesh as it stands for Medical Subject Headings, sometimes stylized as MeSH.
Here is an example: A heart attack my be called an acute myocardial injury or myocardial infarction. In essence, these different terms means the same thing, but the Mesh term chosen for this concept is myocardial infarction, so regardless of if authors refer to this concept in their titles or abstracts as myocardial injury, it will still be tagged with the Mesh term of myocardial infarction. You can see what Mesh terms represent a larger concept in the Mesh database. Try searching for a term and exploring its Mesh entry.
When you do a simple search in PubMed, Automatic Term Mapping is applied, and in that process PubMed automatically finds the Mesh term the keyword you entered is associated with, if there is one. If I search heart attack as a keyword and look in the search details of the advanced search page, it will show that it automatically searched the Mesh term of myocardial infraction as well as the word heart attack in different ways combined with the field tag of All Fields.
"myocardial infarction"[MeSH Terms] OR ("myocardial"[All Fields] AND "infarction"[All Fields]) OR "myocardial infarction"[All Fields] OR ("heart"[All Fields] AND "attack"[All Fields]) OR "heart attack"[All Fields]
here is a question then:
If Mesh terms are supposed to index all of the articles in PubMed on a given topic, why would I need to search in any other way?
The answer here is that Mesh terms aren't perfect. Sometimes an article gets assigned the wrong Mesh term, or no Mesh term at all. They are a helpful tool, but may not capture everything you need. So for a search you'll often want to combine a search in the Mesh field and a search in other fields like [Title/Abstract]. For example, for heart attack, I might try this search: myocardial infarction[Mesh] OR myocardial infraction[tiab] OR myocardial injury[tiab] OR heart attack[tiab]