Medical Subject Headings (MeSH)
MeSH subject searching is a unique feature of health and medical literature. This guide is intended to explain how it works and the advantages of using MeSH headings when searching for information.
|
Background information on MeSH: The MeSH hierarchy - how the headings are arranged What is the difference between searching using MeSH and searching by Keyword? |
| Searching in Medline (Ovid) using MeSH:
Map term to Subject Heading feature in Medline |
| Further help and links |
MeSH stands for "Medical Subject Headings". It currently provides a vocabulary or list of over 26,000 terms which can be used to describe very precisely the content of medical documents (such as journal articles). The MeSH vocabulary is a distinctive feature of the Medline database produced by the National Library of Medicine (NLM).
NLM indexers examine articles and other publication types and assign the most specific MeSH headings that appropriately describe the subject discussed.
Indexers can also assign Subheadings to further describe a particular aspect of a MeSH topic. For example:
| MeSH heading | Subheadings |
|
Diabetes Mellitus, Type 1 |
These include: Complications, Diagnosis, Drug Therapy, Immunology |
Below is an example of a complete reference in Medline (OvidSP) showing the journal article details and the list of MeSH headings (some with subheadings) assigned to it by the NLM Indexers:
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In the illustration above the indexers have assigned subheadings to the MeSH headings Cornea, Intraocular Pressure, Sclera and Visual Acuity.
The MeSH Hierarchy - how the headings are arranged
All the subject terms are arranged in a logical "tree" structure that originates with 16 main categories or branches. Each category is further divided into subcategories.
The major categories are:
| A | Anatomy |
| B | Organisms |
| C | Diseases |
| D | Chemicals and Drugs |
| E | Analytical, Diagnostic and Therapeutic Techniques and Equipment |
| F | Psychiatry and Psychology |
| G | Phenomena and Processes |
| H | Disciplines and Occupations |
| I | Anthropology, Education, Sociology and Social Phenomena |
| J | Technology, Industry, Agriculture |
| K | Humanities |
| L | Information Sciences |
| M | Named Groups |
| N | Health care |
| V | Publication Characteristics |
| Z | Geographicals |
Go to http://www.nlm.nih.gov/mesh/trees.html for a fuller breakdown of the MeSH "tree" structures.
Example of MeSH Hierarchy
Below is an example of part of the hierarchy/ "tree" structure for the MeSH heading Heart Diseases. The narrower terms are indented under the broader terms.
A + sign beside a term indicates there are further, narrower terms. Simply click on the + sign to view them.
A - sign indicates all narrower terms are displayed.
The tree display allows you to:
What is the difference between searching using MeSH headings and searching by Keyword?
Using MeSH:
1. When you search using MeSH headings only the MeSH Subject Headings section of the record in the database is searched as illustrated below:
2. MeSH directs the user to the preferred subject heading. It also provides tools to locate related terms and to specify the focus of the article. For example:
If the user searches for the terms pressure sore, he/she will be directed to the MeSH heading pressure ulcer as will users who search for the terms bed sore or decubitus ulcer.
3. MeSH headings reflect current usage of medical terms.
4. Using MeSH headings will make searching more
Keyword Searching (where you simply type in your search terms):
1. Keyword searching finds words or phrases exactly as they are entered. It will not locate synonyms. Normally the database will search for your terms in the Title, Original Title, Abstract, Subject Heading, Name of Substance and Registry Word areas (fields) of each record.
In the example below a keyword search has been carried out on the search terms pressure sore. This record has been retrieved as the exact terms appear in the title of the record:
2. You may have to search by Keyword if there is no MeSH heading to describe your search concept - in the case of new or obscure topics. Please also note that indexers do not assign MeSH headings to every word in the abstract.
Searching in Medline (OvidSP version) using MeSH headings:
You can access Medline as follows:
Log on to the Portal at portal.ulster.ac.uk ► Click on the Learning Resources tab ► Click on Databases, displayed in the Key Services section ► Click on M in the A-Z list of databases ► Scroll down to the row of information on Medline (Ovid) ►Click on the name ►Click on Proceed.
By default the database should open at the Advanced Search option.
Enter your search term(s) in the search box, ensure that the Keyword search option has been selected and that the tick is displayed in the checkbox next to Map Term to Subject Heading. Click on Search as illustrated below:
The database maps your search term(s) over to the preferred terminology, the MeSH heading, used in the database to describe this topic. In this example pressure sore is mapped over to the Medical Subject Heading Pressure Ulcer :
Scope notes, Explode and Focus features
Clicking on the Scope icon 
will give a definition of the MeSH heading. This is the Scope information available for heading Pressure Ulcer:
Explode feature
Exploding a MeSH heading will:
To view these narrower, more specific terms click on the Subject Heading:
Below is the "tree" for Foot Diseases:
In the screenshot below you can see the difference in the number of results retrieved:
In Search Set 1 the MeSH heading, Foot Diseases, has not been exploded.
In Search Set 2 the heading has been exploded to include all of the narrower terms, resulting in a greater number of records retrieved.
Focus feature
You can use the Focus feature to limit your search to those documents in which your MeSH heading is considered the major point of the article. This will reduce the number of records found.
Please use the Focus feature with caution: Focusing a MeSH heading may result in the loss of useful records. Each article indexed is given 10-20 subject headings. Only headings that specifically describe the article are given Focus status. The screen shot below shows the Medical Subject Headings assigned to an article on Diabetes Mellitus. The asterisk * indicates the Focus terms - you can see that only a small number of terms are allocated this status in the record.
As mentioned at the start of this guide, the National Library of Medicine indexers can also assign Subheadings to further describe a particular aspect of a MeSH topic. You can apply one or more of these subheadings to your search. In the screenshot below click on the Continue button to view the list of subheadings for Pressure Ulcer.
Tick the checkboxes next to those subheadings you wish to select. If you do not wish to limit to a specific subheading or aspect of the topic you should tick the Include All Subheadings checkbox.
In the example below, the search on the MeSH heading Pressure Ulcer has been limited to the subheading Prevention & Control. Only those articles which are about this aspect of pressure ulcers will be retrieved.
For more help on using MeSH headings please contact a member of the Life and Health Sciences Library team. Contact details are displayed at the bottom of the page.
More information on MeSH headings is available at:
The Basics of Medical Subject Headings (MeSH) in MEDLINE/PubMed.