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MSH (MeSH) - Synopsis

Search MSH in the UMLS Metathesaurus
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The Medical Subject Headings (MeSH®) are developed and maintained by the U.S. National Library of Medicine (NLM).

The MeSH thesaurus is a controlled vocabulary used for indexing, cataloging, and searching for biomedical and health-related information and documents. It enables retrieval systems, such as PubMed, to provide subject searching of data.


The three basic types of MeSH records are Descriptors, Qualifiers (subheadings), and Supplementary Concept Records (SCRs).

There are four Descriptor classes:

  • Class 1 Descriptors - Main Headings
  • Class 2 Descriptors - Publication Types
  • Class 3 Descriptors - Check Tags
  • Class 4 Descriptors - Geographics

Descriptors are organized in a hierarchical, numbered tree structure which enables browsing from broader to narrower topics.

Subheadings are used with Descriptors to group citations for specific aspects of a subject (ex. Liver/drug effects).

SCRS aid indexing of chemicals, drugs, and similar concepts. There are four classes of SCRs:

  • Chemicals
  • Protocols
  • Diseases
  • Organisms

MeSH is continually updated by NLM health science subject specialists. New terms from scientific literature and research can be recommended for addition to MeSH.

Metathesaurus Scope
The Metathesaurus also includes the following MeSH translations:

  1. Croatian
  2. Czech
  3. Dutch
  4. Finnish
  5. French
  6. German
  7. Italian
  8. Japanese
  9. Latvian
  10. Norwegian
  11. Polish
  12. Portuguese
  13. Russian
  14. Spanish
  15. Swedish

The MeSH vocabulary is designed for use by NLM for indexing and searching the MEDLINE database of journal citations and cataloging the NLM collection.

MeSH is used by indexers, subject catalogers, online searchers, and in retrieval systems.

Update Frequency
A revised MeSH vocabulary is released annually; Descriptors and Qualifiers are updated annually while Supplementary Concept Records are updated continuously.

Metathesaurus Update Frequency
MeSH is an updated source in each Metathesaurus release. Descriptor and Qualifier changes appear in the November release while Supplementary Concept Record changes appear in each release.

Sites Consulted

  1. Medical Subject Headings [Internet]. Bethesda (MD): National Library of Medicine (US); 1999 September 01 [reviewed 2018 Apr 26; updated 2018 Apr 26]. Preface; 2014 Aug 06 [reviewed 2016 Nov 07; updated 2016 Nov 07; cited 2018 May 09]. Available from:; MeSH record types:; Use of MeSH in online retrieval: