Medical Subject Headings

MeSH vocabulary is divided into four types of terms. The main ones are the "headings" (also known as MeSH headings or descriptors[2]), which describe the subject of each article (e.g., "Body Weight", "Brain Edema" or "Critical Care Nursing"). Most of these are accompanied by a short description or definition, links to related descriptors, and a list of synonyms or very similar terms (known as entry terms). MeSH contains approximately 30,000 entries (as of 2022) and is updated annually to reflect changes in medicine and medical terminology.[3] MeSH terms are arranged in alphabetic order and in a hierarchical structure by subject categories with more specific terms arranged beneath broader terms. When we search for a MeSH term, the most specific MeSH terms are automatically included in the search. This is known as the extended search or explode of that MeSH term. This additional information and the hierarchical structure (see below) make the MeSH essentially a thesaurus, rather than a plain subject headings list.[4]

The second type of term, MeSH subheadings or qualifiers (see below), can be used with MeSH terms to more completely describe a particular aspect of a subject, such as adverse, diagnostic or genetic effects. For example, the drug therapy of asthma is displayed as asthma/drug therapy.

The remaining two types of term are those that describe the type of material that the article represents (publication types), and supplementary concept records (SCR) which describes substances such as chemical products and drugs that are not included in the headings (see below as "Supplements").[5]

In MEDLINE/PubMed, every journal article is indexed with about 10–15 subject headings, subheadings and supplementary concept records, with some of them designated as major and marked with an asterisk, indicating the article's major topics. When performing a MEDLINE search via PubMed, entry terms are automatically translated into (i.e. mapped to) the corresponding descriptors with a good degree of reliability; it is recommended to check the 'Details tab' in PubMed to see how a search formulation was translated. By default, a search for a descriptor will include all the descriptors in the hierarchy below the given one. PubMed does not apply automatic mapping of the term in the following circumstances: by writing the quoted phrase (e.g., "kidney allograft"), when truncated on the asterisk (e.g., kidney allograft *), and when looking with field labels (e.g., Cancer [ti]).[5]

At ClinicalTrials.gov, each trial has keywords that describe the trial. The ClinicalTrials.gov team assigns each trial two sets of MeSH terms. One set is for the conditions studied by the trial and the other for the set of interventions used in the trial. The XML file that can be downloaded for each trial contains these MeSH keywords. The XML file also has a comment that says: "the assignment of MeSH keywords is done by imperfect algorithm".

The top-level categories in the MeSH descriptor hierarchy are:

• Anatomy [A]
• Organisms [B]
• Diseases [C]
• Chemicals and Drugs [D]
• Analytical, Diagnostic and Therapeutic Techniques, and Equipment [E]
• Psychiatry and Psychology [F]
• Phenomena and Processes [G]
• Disciplines and Occupations [H]
• Anthropology, Education, Sociology and Social Phenomena [I]
• Technology, Industry, and Agriculture [J]
• Humanities [K]
• Information Science [L]
• Named Groups [M]
• Health Care [N]
• Publication Characteristics [V]
• Geographicals [Z]

• Medical classification
• Medical literature retrieval

Wikidata has the property:

• MeSH descriptor ID (P486) (see uses)

• Medical Subject Heading Home provided by National Library of Medicine, National Institutes of Health (U.S.)
• MeSH tutorials
• Automatic Term Mapping
• Browsing MeSH:
  • Entrez
  • MeSH Browser
  • Visual MeSH Browser mapping drug-disease relationships in research
  • Reference.MD
• of qualifiers – 2009