This 12-minute video is an introduction to the development, structure and use of the MeSH® vocabulary. The video may be of particular interest to searchers of MEDLINE®/PubMed®, and is used in the PubMed search classes offered by NLM and the National Training Center and Clearinghouse.
The U.S. National Library of Medicine is part of the National Institutes of Health in Bethesda, Maryland.
In 1960, NLM created the MeSH vocabulary.
MeSH stands for Medical Subject Headings.
The MeSH vocabulary is similar in concept to keywords on other systems. MeSH vocabulary includes four types of terms: Headings, Subheadings, Supplementary Concept Records, and Publication Types.
A MeSH heading represents a concept found in the biomedical literature. MeSH headings can be broad in scope, such as the “Musculoskeletal System,” or narrow in scope such as the heading, “Eyelashes.”
The MeSH vocabulary is updated yearly. New headings are carefully selected for inclusion based on their importance to clinical care and research, and their significance and usage in the literature.
MeSH covers a variety of biomedical subjects as well as many non-clinical topics. These subjects make up different branches of what is known as the MeSH Tree Structure.
The tree has 16 main branches, or categories, including Anatomy, Organisms, Diseases, Chemicals and Drugs, Humanities, Health Care and Geographic Locations.
The MeSH tree structure is a hierarchy. Headings are positioned in the tree according to their relationship to other headings.
Look at the heading “Eye” in the Body Regions branch under “Anatomy.” Notice that the headings, “Eyebrows” and “Eyelids” are indented under “Eye” because these specific parts of the eye are narrower in scope. Also, see that the more specific heading, “Eyelashes” is indented quite logically under “Eyelids.”
Many headings occur in more than one branch of the tree. Looking again at the heading, “Eye,” we see that in addition to being in the “Body Regions” branch it is also found in the “Sense Organs” branch.
The National Library of Medicine produces MEDLINE, a database of citations to biomedical journal articles. MEDLINE is widely respected because the citations are enhanced with MeSH vocabulary terms. MEDLINE is the largest component of the PubMed system. PubMed users can use MeSH terms in their searches.
Subject specialists in anatomy, chemistry and other related fields are trained by NLM to become indexers for the National Library of Medicine’s MEDLINE database. Indexers, many of whom are language specialists, review journal articles and assign the most specific MeSH headings necessary to reflect the central concepts discussed in the articles. When there is no single specific MeSH heading for a concept, the indexer will use the closest, more general MeSH heading available. The indexer will assign as many MeSH headings, usually ten to fifteen, as appropriate to cover the topics of the article. This allows the searcher a variety of subject access points to each article.
An asterisk is used to indicate the MeSH concepts that are considered to be the main point of the article.
Indexers must also assign MeSH headings to describe the group or person being studied. These “check tags” as they are called, specify human and animal studies, male and female studies, the age of the group or individual studied, and the type of the article being indexed.
The type of the article being indexed is noted using special MeSH terms called “Publication Types.” The Publication Type, “Journal article” is the most common item cited in MEDLINE.
Subheadings are another type of specialized MeSH term that are used in combination with the MeSH headings. There are over eighty Subheadings that can be used by indexers to further identify a particular aspect of a MeSH concept. For example, the subheading “Diagnosis” is used with MeSH terms for diseases when the article is about the diagnosis of that disease.
This article, about symptoms of asthma has been indexed with the MeSH heading “Asthma” and the subheading, “diagnosis.” You can also use Subheadings in your searches to help make your retrieval very specific. For example, if you wanted to search for MEDLINE citations to articles about headaches, but specifically about treating headaches, you can search for the MeSH heading “Headache” and the subheading, “therapy.”
Articles are indexed using the most specific MeSH headings available, and you should follow this same principle when selecting headings for your search. For example, if you were searching for articles about the lip, you should use the specific heading “Lip,” not the more general heading, “Mouth.”
In another example, to retrieve citations to articles about inflammation of the urinary bladder, use the heading “Cystitis,” not the broader term, Bladder Diseases.”
The Entrez MeSH Database can help you find MeSH terms and search with them in PubMed.
Let’s use the MeSH database to look for the concept of Gastroparesis, a stomach disorder.
We see that there is a MeSH term for this concept. A definition is provided. Clicking on the MeSH term takes us to more information about this term.
If a term was added to the MeSH vocabulary after the early-1960’s, the year of introduction is displayed. This term was introduced in 1995.
A section on the screen called, “Previous Indexing” indicates how articles on this topic may have been indexed prior to 1995.
Here are the subheadings that are found with the MeSH heading Gastroparesis in MEDLINE. You can use the check boxes to select any that you want to use to focus your search.
We can search this term when it is the major topic of an article. That will help improve the relevancy of the retrieval.
Many MeSH headings have Entry Terms. Entry terms are considered to be synonymous, or close in scope to the MeSH term. PubMed recognizes these terms so that, if you search with an Entry Term, the appropriate MeSH term will be included in the search.
Let’s show this in PubMed. If we search for gastric stasis, PubMed will recognize this as an entry term for Gastroparesis and citations with that heading will be retrieved. This ability to use variant names for a concept allows invaluable flexibility for searchers.
Back in the MeSH database record for Gastroparesis… if we scroll down we see the position of this term in the hierarchy. This lets you see broader as well as narrower headings. This term has been placed in two branches of the MeSH tree. This is the placement of the term in the Digestive System Diseases branch, and this is the placement of the term in the branch for Pathological Conditions, Signs and Symptoms. We can see broader terms, but there are no narrower terms under Gastroparesis.
Let’s use the MeSH Database to find a MeSH heading to use in a search for the concept of “light therapy.”
The first thing to determine is whether or not this concept is covered by MeSH.
Searching for this term in the MeSH Database, the best match is usually near the top of the search results.
Here is the Scope Note that provides an explanation or definition of the heading. This can help us decide if this is the correct concept for our search. This one looks good.
Let’s take a closer look at the concept, “Phototherapy.”
We see this concept was introduced in MeSH in 1981. To see how this concept would have been indexed prior to that year, we can look at the Previous Indexing information. There are two terms that may have been used singly or in combination depending on the subject of the article.
Notice the Entry Terms. There are several for this concept, including the term we used for browsing. Remember, any of these can be used to search PubMed for this MeSH concept.
Here are the subheadings that indexers have assigned and searchers can use with this concept.
Here is the MeSH tree representation that includes this term.
You can see the heading in relation to other headings. Notice how this concept is under two branches of therapeutics: Physical Therapy Techniques, and Rehabilitation.
Also notice that there are more specific headings indented under “Phototherapy,” including Color Therapy, Heliotherapy and Ultraviolet Therapy.
When searching a broad term in PubMed, indented headings are included. This is known as the automatic explosion feature. In this example, a search of “Phototherapy” will retrieve citations for articles indexed with these more specific terms.
The term, PUVA Therapy, has a plus sign indicating that there are more specific terms indented under it. To see these terms, we will link to the record for this term in the database.
Scrolling down to the display of the hierarchy we see the indented term, Photopheresis. It does not have a plus sign, so there are no terms indented under it.
In addition to MeSH headings, subheadings and publication types, the MeSH vocabulary also includes over one hundred and eighty thousand Supplementary Concept records. These terms represent chemicals and substances that are mentioned, in a significant way, in an article.
“Supplementary Concepts” are assigned by indexers, can be used by searchers, and display on MEDLINE citations as “Substances.”
New concepts continually appear in the published literature. Therefore, the MeSH vocabulary must be updated at regular intervals.
As you can see, the MeSH vocabulary is an important part of the National Library of Medicine’s mission to index the biomedical literature and to facilitate literature searching.
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