Overview

In the fall of each year NLM performs maintenance to MEDLINE data, known as Annual MeSH Processing (AMP). AMP encompasses extensive changes to MEDLINE citations. The primary function of AMP is to update the Medical Subject Headings (MeSH) on existing MEDLINE citations to conform with the upcoming version of MeSH, which is released annually in early December. Changes are made to MeSH descriptors (main headings), qualifiers (subheadings), and Supplementary Concept Records (SCRs). Other global changes to MeSH headings may be made during AMP as well.

The eight MeSH Update reports listed below detail the changes to MeSH terms that are performed during AMP. These procedures usually start in early December when the annual MeSH update files are released and are targeted for completion by the middle of December. When AMP activities are complete, the new version of MEDLINE, with the new year's MeSH Headings, is loaded into PubMed, and the regular MEDLINE/PubMed update schedule resumes. At this point PubMed uses the new year's MeSH vocabulary in the MeSH translation tables and the MeSH database.

Each of the MeSH Update Reports are cumulative, containing data for all years, starting from 2023. Each report contains a Year field, identifying changes to MeSH for that release year.

The resources listed below provide additional information on MeSH and Annual MeSH Processing (AMP).

Annual MeSH Processing (AMP) Resources

NLM Technical Bulletin article on Annual MeSH Processing for 2026

Additional MeSH Resources

Medical Subject Headings (MeSH)

MeSH XML Data Elements

MeSH Browser

MeSH Qualifiers with Scope Notes

MeSH New Headings with Scope Notes (2023)

MeSH Publication Types