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 Chemical Records (SCRs).
There are four Descriptor classes:
Most Descriptors are organized in a hierarchical, numbered tree structure which enables browsing from broader to narrower topics. Check tags are the exception and do have a hierarchical structure.
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:
MeSH is continually updated by NLM health science subject specialists. New terms from scientific literature and research can be recommended for addition to MeSH.
MeSH is also included in RxNorm.
The Metathesaurus also includes the following MeSH translations:
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.
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.