Responsible Literature Searches

Browse Literature for More Keywords

One way to find more keywords is by simply skimming existing literature. In the early stages of research, it can be helpful to run simple searches for the key concepts you identified in your research question. You can do this in a database like PubMed or a search engine like Google Scholar.

In the below example, the keywords from Question 1 were searched in PubMed (using Boolean operators which will be discussed in the next page) and produced 18 results with the below example listed first. From here, we can identify some author supplied keywords at the bottom of the abstract and even a potentially helpful term within the abstract. These are terms we hadn't thought of originally but can go back and add now that we know they exist.

Use Controlled Vocabulary as Keywords

Since we know how to find keywords, we also know that there are many ways of describing the same concept (i.e. TENS, "transcutaneous electrical nerve stimulation" or “heart attack,” “myocardial infarction”).

Due to the variation of term use, some databases use a single, authoritative term which we refer to as controlled vocabulary (a.k.a. “subject heading", "index term", or "thesaurus" depending on the database).

The controlled vocabulary terms that are associated with an article are determined by subject specialists who review each article that is to be included in the database. These specialists read the article, decide what it is mostly about, and assign a controlled vocabulary term to the citation. You can think of controlled vocabulary as "tags" for an article.

You as the searcher can then use the controlled vocab terms as synonyms to your keywords in order to find additional and more accurate results. Click on the next tab, "MeSH" to learn more about the controlled vocabulary used in PubMed.

Using MeSH (PubMed's Controlled Vocabulary)

The controlled vocabulary used by PubMed are called Medical Subject Headings or MeSH. You can find MeSH terms by searching for your concept in the MeSH Database.

You can also find related MeSH terms by scrolling to the bottom of a highly relevant PubMed article to the "MeSH Terms" section and choose any related terms from here. (Demonstrated in the example below).

When opening a MeSH term from the article or within the MeSH database you will find additional information about the term. Below is an example of the MeSH term entry for Dysmenorrhea.

Within the term listing for Dysmenorrhea (above), we find a few pieces of information related to this MeSH term.

1. We see the MeSH term itself "Dysmenorrhea" with a description of the term below it, this is standard for every MeSH term
2. We can also add subheadings if we want to narrow our use of this term within a search. For example, by limiting to the subheading, "surgery," we will only pull results that talk about Dysmenorrhea in the context of surgery.
3. MeSH terms also include entry terms. Entry terms are alternative ways of saying the MeSH term. For example, we see an entry term here is "Menstrual Pain," so if a searcher were to plug "Menstrual Pain" in PubMed, articles including "Dysmenorrhea" as a MeSH term will be picked up in the results even if the article itself doesn't explicitly use the term "Menstrual Pain."
4. Finally, we can use the MeSH Tree to broaden or narrow our search. The further up the tree, the broader the term, and the lower the term is on the tree, the narrower the topic. In this example, we can see that "Pain" is a broader concept/term than the more specific condition of "Dysmenorrhea."

Why Use Both Keywords and Controlled Vocabulary?

Controlled vocabulary doesn't cover it all.

Skilled researchers always use a combination of controlled vocabulary and keywords within their search strategies. This is because using both will ensure that your search is as comprehensive as possible.

MeSH is handy because it includes any article that is about the concept the term represents, even if the article never actually uses that term within the title or abstract. This also means that if an article hasn't been reviewed and assigned a MeSH term yet, you will not see it in the results list by just using MeSH terms.

Keywords don't cover it all.

Conversely, if we were to just use keywords, we would miss any article that may be about our concept but doesn't include the exact keyword we used. Again, controlled vocabulary terms include any article that is about the concept the term represents, even if the article never actually uses that term within the title or abstract. Using only keywords and skipping the controlled vocabulary could cause us to miss out on a substantial amount of literature.