What is Mesh ?

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 when searching for information.


  MeSH is the acronym for "Medical Subject Headings". It provides a vocabulary of some 15,000 terms which can be used to describe very precisely the content of medical documents. The MeSH vocabulary is a distinctive feature of the MEDLINE database produced by the National Library of Medicine (NLM). NLM indexers examine articles and assign the most specific MeSH heading(s) that appropriately describes the subject discussed. As many as 15 headings may be assigned to an article. Indexers can also assign Subheadings to further describe a particular aspect of a MeSH topic. Examples of Subheadings are: diagnosis, surgery, metabolism, pathology,

  In addition to assigning MeSH terms that describe the topic of the article, the indexer provides terms that reflect:

  • the age group of the population studied
  • the nature of the studies e.g. human, animal, male, female
  • the material represented (Publication Types) e.g. Clinical Trials, Editorial, Review


  All the subject terms are arranged in a logical "tree" structure that originates with 15 main categories or branches. These branches then have others branching off them and so on with each branch becoming more and more specific.
The major categories are:
E-Analytical, Diagnostic and Therapeutic Techniques and Equipment
F-Psychiatry and Psychology
G-Biological Sciences
H-Physical Sciences
L-Information Sciences
M-Named Groups
N-Health Care


  Below is an example of part of the hierarchy that includes the term Face. The narrower terms are indented under the broader terms.
A + sign beside a term indicates there are further, narrower terms. Simply click on the + to view them.
A - sign indicates all narrower terms are displayed


  The tree display allows you to:

  · View subject headings in their hierarchical context

  · View surrounding headings, ensuring that the best term may be searched

  · Display subject headings in all contexts


  Searching MeSH vs Keyword



  Searches the Subject headings field only

  Searches the title and abstract fields

  MeSH directs the user to the preferred subject headings. It also provides tools to locate related terms and to specify the focus of the article.

  Finds words or phrases exactly as they are entered, unless a word is truncated.
It will not locate synonyms.

  Reflects current usage of medical terms.

  Should be used when there is no Subject heading to describe a concept - in the case of new or obscure topics.

Using MeSH headings will make searching more;

  1. Relevant ie only information on the subject will be retrieved. A keyword search will retrieve all articles in which the word is used even though the focus of the article may not be that subject. For example searching AIDS will find articles on the medical condition but also articles on hearing aids, clinical aids etc. Using Acquired Immunodeficiency Syndrome (the MeSH heading) will limit the search to the medical condition.

  2. Consistent ie MeSH ensures that subjects are consistently indexed under the same headings.

  Scope notes


  Clicking on the Scope icon will give a definition of the Subject Heading.



  Exploding a term will:

  · Find all articles on a topic, both specific and general

  · Will result in a greater number of records found.

  Articles are indexed to the most specific term available in the Thesaurus. For example a search on a general term such as Diabetes Mellitus will only find articles of a general nature. By exploding the term the results will include specific terms in that branch of its subject “tree”.

  Example search under Diabetes Mellitus:


  Search 1 – Diabetes Mellitus
Finds only those articles that consider Diabetes Mellitus in a general way.

  Search 2 – exp Diabetes Mellitus
Finds articles on Diabetes Mellitus as well as the more specific terms displayed in the tree below.



  Focusing a term will:

  · Find only articles on that specific term
· Reduce the number of records found

  Note: Focusing a search term(s) may result in the loss of useful citations. Each article indexed is given 10-20 subject headings. Only headings that specifically describe the article are given Focus status.

  Below are the subject headings assigned to an article on Diabetes Mellitus. The * indicates the Focus terms.


  It is NOT recommended to Focus a search when:

  · Performing a literature review

  · Searching a new or obscure topic which may only have a small number of articles.


  At the start of a search

  When a term is entered the MeSH thesaurus is searched to find the preferred MeSH term or list of related headings. The searcher must then select the most appropriate headings. One term at a time should be “mapped” on to the MeSH thesaurus to view all possible headings.

  When viewing retrieved citations

  It is possible to display all the MeSH headings assigned to one article. For example in OVID select Complete Reference beside the summary of the article to view its headings.

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