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What's a MeSH Search?
- You can search PubMed by using Medical Subject Headings (MeSH), also known as MeSH terms. PubMed employs experts who read articles and decide which MeSH terms best describe the topics covered, and then add those terms to the article's PubMed record. MeSH terms are selected from a reputable thesaurus with the aim that all articles on the same topic can be identified by the same term. Therefore, MeSH searches often retrieve more precise sets of results than standard keyword searches. To help you identify MeSH terms, you could search PubMed for a reputable article that you already know. Then click its title to enter its full PubMed record where you may find MeSH terms listed.
- How MeSH searches work: when you search using a MeSH term, PubMed also searches for any equivalent "entry terms" at the same time. Therefore, MeSH searches reduce the need for you to enter alternative search terms for the same concept e.g. a search for avian influenza also finds bird flu. If you're doing a systematic review, it's best practice to do both keyword and MeSH searches in order to be as thorough as possible. Combine the results of the separate searches in the Advanced Search screen (Search History section).
Searching PubMed's MeSH thesaurus
- To identify which words/phrases exist as MeSH terms, use the MeSH search page (there's a link to this page near the bottom of the PubMed screen). Generally, you only need to search for one MeSH term to represent each concept within your research question (don't use asterisks). If the term exists in the MeSH thesaurus, either a full record will open automatically or a list of alternative terms will appear (click on a listed term to open its full record).
We'll use the following as an example of a research question:
Evaluate practices for gaining informed consent where mental competency is a potential issue.
The two concepts for which we're searching for MeSH terms are informed consent and mental competency.
- To select your MeSH terms: It's best practice to click the MeSH result in which you're interested (note the descriptions) and enter the full record for that term. You can scroll down the record see how where the term sits within the thesaurus "tree". This may inspire you to select narrower or broader terms instead (you can opt to either include/exclude all narrower terms).
You may also find a list of entry terms (i.e. alternative MeSH terms which have the same/similar meaning) so by searching for one term, PubMed will also retrieve records featuring all of its entry term equivalents.
For a more focused search, you can also select/tick subheadings near the top of the record. Depending on the topic, these include for example, ethics, standards, abnormalities, adverse affects, diagnosis, drug therapy, epidemiology, genetics, metabolism, microbiology, nursing, psychology, prevention, rehabilitation and therapy.
Finally, there's an option just below the subheadings for ticking a box to limit your results to those in which the MeSH term represents the major focus of an article.
- To add your MeSH terms to the 'Search Builder':
If you're searching for just one MeSH term per concept: After you choose each term that you want to combine, select AND from the drop-down menu next to 'ADD to search builder' to the right of the screen. Once all the terms appear in the 'query box', click 'Search' to retrieve your results.
If you're searching for alternative MeSH terms for the same concept: After you select each term, select OR from the drop-down menu next to 'ADD to search builder' to the right of the screen (so at least one term will be present in each search result). Once all the terms for one of the concepts appear in the 'Search Builder' box, click 'Search' to retrieve an initial set of results. Return to the MeSH search screen to search for the next concept. Finally, follow the instructions for combining the results of all the searches. Given that many MeSH terms automatically "map" to alternative "entry" MeSH terms with the same/similar meaning, you may not need to use this method. (refer to point 2 above).
- If the MeSH thesaurus doesn't include a term that you searched for (or it doesn't provide a sufficiently close alternative), enter the term(s) as a keyword(s) within the same 'search builder' box that you're using to build up your MeSH terms. If you're entering multiple keywords for the same concept, enter the word OR in between each one and wrap that entire set of keywords within a single set of brackets. PubMed can search for a combination of keywords and MeSH terms within the same set of search terms. Note the advice on using speech marks and asterisks within the keyword search tab in this guide,
- You can opt to combine the results of a MeSH search with a results of a keyword search. To find out how to do this, refer to combining searches.