What are MeSH terms?
MeSH terms are the NLM's controlled vocabulary. A controlled vocabulary is a specified, pre-determined collection of terms (about 30,000 in this case). You cannot make up or add your own MeSH terms. Indexers (real live people!) read each article and tag them with a handful of MeSH terms. Then, when we search on that term, all articles tagged with that term are retrieved.
Why use a controlled vocabulary? The magic lies in fact that the number of terms is restricted, which helps overcome the fact that these databases do not have an intuitive search like Google does. In Google, you can search "used cars for sale" and you'll get "used SUVs for sale," "used Jeeps for sale," etc. These databases are not like that - you get articles that correspond to the terms you searched on. Using a controlled vocabulary helps overcome that.
Example: Let's say you're interested in articles about pressure wounds. You'd also be interested in articles that use the phrases "pressure sores," "pressure injuries," and "pressure ulcers." Since the databases aren't intuitive, if you search on "pressure wounds" and the article only uses "pressure injuries" you won't get that article (you didn't tell the database you wanted articles about pressure injuries!). You would have to create a search string that contains all of the phrases above.
However - the controlled vocabulary would have only one term for this topic. Here is "Pressure Injuries." The indexers who read an article about "pressure injuries" would tag that article with the Subject Heading "Pressure Injuries." If the next article mentions only mentions "pressure wounds" it would also be tagged "Pressure Injuries." If the next articles says "bedsores" it would also be tagged with "Pressure Injuries."
Then, by searching the subject heading "Pressure Injuries," you will get articles that use the words "pressure wounds," "pressure sores," "pressure injuries," and "pressure ulcers" - and even bedsores.
How to Search Cochrane Using MeSH Terms
To search using MeSH terms in Cochrane, you must be logged into your account. You can do so (or create an account) using the link in the upper right corner. Click "Advanced search" without putting any words into the search box.
On the next screen, click "Medical terms (MeSH)"
In the first box on the next screen, click your search term ("Pressure Ulcer" in this case). In the second box, it is usually best to leave the default "Explode all trees" selected. In the third box, click "Add to search manager."
This will bring you back to the Advanced Search page, and the first box will be populated with the MeSH terms. On subsequent lines, type in your keywords as shown in the image below. When all terms related to your first concept are entered, combine them using OR in the next line. You will have to type in the characters (e.g. the # sign, then the number, etc.).You want to use OR here because you want articles that were 1) tagged with the MeSH term or have the keywords in 2) or 3).
Repeat this process for the next concept(s), again using OR to combine them.
When all terms are entered, it's now time to combine them using AND. That way we'll get articles that talk about pressure wounds AND inpatients.
To get to your results, click on the final number on the bottom right; in this case 1369. You will be brought to a screen similar to the one below. You can see there are 8 Cochrane systematic reviews and 1361 trials. To see each type, click the tab. To export them, select the ones you want (or Select All) and click Export. If you're exporting to a citation manager (Covidence, Zotero, etc.), choose RIS. You can also export in CSV file if you want a spreadsheet. Your file will be downloaded and ready to go!
If you want a reproducible search strategy, hit the back button until you see the screen with the search history and then choose. "Print Search History." From that screen you can also save this search.
