Bridging the Gaps Research Program: PubMed

Resources for students that are a part of the Bridging the Gaps research program

Helpful Links

What is PubMed

What is PubMed?

  • A database of more than 30 million citations to articles in the fields of biomedicine and health.
  • Used by millions of users each day, including health professionals and others engaged in:
    • research
    • public health
    • health policy development
    • clinical care
    • patient advocacy
    • educational activities
  • PubMed is fully responsive and mobile-friendly!


Watch: Accessing PubMed@USC (1:53)

This video will cover:

  • What PubMed is
  • Why students and faculty should access PubMed through the USC Libraries website

Beginning the Search

Watch: PubMed Basic Search (3:12)

The video will cover:

  • How to conduct a basic search in PubMed
  • How to filter and save results

Advanced Searching: Medical Subject Headings (MeSH)

What are MeSH terms?

Medical Subject Headings (MeSH) are terms that PubMed uses to tag articles with. PubMed is a human-curated database, meaning that all articles in PubMed have been read by an indexer at the National Library of Medicine. Once they have finished reading an article, they consult the MeSH database to find a relevant MeSH term and tag it to the article's record. You can use MeSH terms in your search query to help retrieve more relevant results.

One of the biggest advantages to using MeSH terms is that all MeSH terms are pre-defined and have synonyms included. MeSH is effective for searching for meaning, rather than only looking for where words appear in the text of the abstract. For example, when we search PubMed for "weight lifting", do we mean the competitive sport or in the context of physical therapy? And how many different ways can we articulate this concept?

Keywords vs. MeSH



  • used for quick searching
  • useful for new ideas, concepts, terminology that may not be widely used.
  • used for precise searching
  • useful for well established concepts and terms
  • encompasses synonyms and alternate spellings

When conducting your own search you will likely use a combination of both keywords and MeSh terms.

NOTE: Most recent articles in PubMed do not yet have MeSH terms attached to them. So, to ensure you can find the most recent literature it is important to combine both MeSH and keywords

MeSH Trees

MeSH terms are related to each other in a hierarchical order. The MeSH tree can be found at the bottom of every MeSH record.

See the MeSH tree example below demonstrating the hierarchical relationship between hepatitis to liver diseases, in general, as well as specific types of hepatitis. The higher in the 'tree' the more broad the term, which will lead to more results. The lower in the 'tree' the narrower and more specific the term is, which leads to less results but that are more specific.

Medial subject heading example tree showing the hierarchical relationship between hepatitis to overall liver diseases as well as specific types of hepatities

Watch the videos below to learn more about the MeSh database

Approximately 15mins total run time

Advanced Searching: Automatic Term Mapping

Basic PubMed Searches Explained

PubMed uses a process called Automatic Term Mapping to determine what you are looking for and matches it to subjects (using MeSH). This helps to expand or narrow your search.

You can examine how PubMed searches and 'translates' your keywords by clicking on the Advanced link below the search box. Scroll down and you will see that PubMed stores your History and Search Details.

PubMed also automatically searches for alternate spellings, such as British English variations.


If we search for the commonly used term "heart attack" we can see how PubMed 'translates' this search to also include "myocardial infarction"

example of searching the term heart attack and automatic term mapping including the term myocardial infarction.

NOTE: It is good practice to check the search details to see what terms are being applied to your search. While Automatic Term Mapping can be helpful, it can also misinterpret your search and include terms that aren't relevant.  For example, if you search for “cold AND zinc,” PubMed will include the controlled vocabulary for "cold temperatures" in the search.

Interactive Tutorial