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PubMed Tutorial from The Levy Library: MeSH: The Key to Medline

MeSH: The Key to MEDLINE

The key to MEDLINE is a controlled vocabulary system called the Medical Subject Headings (MeSH).

MeSH terms impose uniformity and consistency to the indexing of biomedical literature and are applied to citations when they are indexed for MEDLINE. This system offers three main advantages:

1. MeSH indexing facilitates the retrieval of relevant articles even when authors have used different words or spellings to describe the same topic. 

For example:  

  • Trisomy 21, Down's Syndrome and Down Syndrome are all possible synonyms for the same topic.  The MeSH term Down Syndrome covers all of the variations - saving you from having to type them all into your search.

  • Krebs Cycle, Tricarboxylic Acid Cycle, and Citric Acid Cycle are all possible synonyms for the same topic.  The MeSH term Citric Acid Cycle covers all of the variations - saving you from having to type them all into your search.

  • Lung cancer, lung tumor, lung neoplasm, and pulmonary cancer are all possible synonyms for the same topic.  The MeSH term Lung Neoplasm covers all of the variations - saving you from having to type them all into your search.

2. MeSH indexing increases the discoverability of citations.  If a citation has no abstract or otherwise does not effectively convey the topic(s) discussed in the article, MeSH indexing allows for discovery of this citation even by basic keyword searching.  

For example:

I run a basic search for chemoembolization and hepatocellular carcinoma.  I am able to find the citation below (PMID: 25376280) only thanks to the MeSH indexing.  Since the term chemoembolization does not appear in the title, abstract, or any other field, prior to when this citation was indexed for MEDLINE it would be missed by my search for chemoembolization and hepatocellular carcinoma.  Only because the MeSH term Therapeutic Chemoembolization has been applied can I locate this record using these search terms.

3. MeSH indexing facilitates searching of both the broad and the narrow simultaneously due to the existence of the MeSH hierarchy.  MeSH Headings, Subheadings and Publication Types are organized in hierarchies, or "MeSH trees".

MeSH logo

At the most general level of the hierarchy are very broad headings such as "Anatomy" or "Mental Disorders".  More specific headings are found at narrower levels of the hierarchy, such as "Ankle" and "Conduct Disorder".  A MeSH term can be part of one or more hierarchies.

For example:

Check out the MeSH entry for Cardiovascular Diseases.  Scroll to the bottom to see the MeSH tree.  If I am interested in smoking and cardiovascular disease then by using the term Cardiovascular Diseases in my search, I will automatically retrieve citations containing the term smoking and cardiovascular diseases as well as smoking and the over 50 more specific types of cardiovascular disease found in the hierarchy (e.g. smoking and cardiomegaly, smoking and hypertension, smoking and vasculitis, etc.)

Each year, MeSH terms are added or changed to define new trends and concepts. For example, in 2013 the terms Proton Therapy and Mitochondrial Degradation were added to MeSH, and the term Phosphoric Acid Esters was changed to Organophosphates.

Professional Indexers Enhance MEDLINE Records with MeSH Descriptors

These descriptors are used, along with other text in citations and abstracts, to find MEDLINE records. 

MeSH descriptors

  • MeSH vocabulary contains four types of descriptors: Headings, Subheadings, Publication Types, and Supplementary Concept Records. 

    In this example, the Publication Type is "Case Reports".
  • Each journal article is indexed with about 10-12 MeSH Headings.

  • About 3 MeSh Headings are designated as a major MeSH topic for the article. Major MeSH headings are marked with an asterisk (*).

    In this example, among the major topics are Anti-Arrhythmia Agents and  Atrial Fibrillation.

  • Articles are indexed with the most specific MeSH descriptor available, helping you to retrieve the most accurate results.

    Example: this article on atrial fibrillation would NOT be described with the broader term, Heart Diseases.

Remember, only MEDLINE records are indexed with MeSH. Records in PubMed that are not in MEDLINE are NOT indexed with MeSH descriptors.

Display MeSH Vocabulary in PubMed

double arrowsDisplay a record's MeSH descriptors by clicking the MeSH Terms link or the double arrows below the MEDLINE citation in PubMed's Abstract view.