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Health Sciences Literature Searching: Narrowing Your Search

A guide to help you search the Health Sciences literature

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Use the following links to jump to a chosen topic to narrow your search:

Search Operator AND

Search Limiters

Subject Headings



Search Operator AND narrows your search by helping you find articles that discuss two different concepts.

What is the Search Operator AND?

Many databases, including CINAHL and PubMed, will automatically insert AND between your search terms. Use the following part of the guide to see how this affects your search.

If you were to look at two topics (A or B) separately, you will find plenty about each article individually. Although that is helpful for general ideas, it is better to look at the shared ground between two different topics.


Thinking about AND can get you to think about how A impacts B, what A has in common with B, and how A and B differ.

Using AND

Let's say we want to know which diseases are carried or caused by insects. Start by listing insects and diseases separately.

Combine the two to see what Insects AND Diseases have in common.

Searching for Insects AND Diseases pulls "Malaria", "Cholera", and "HIV/AIDS" because those are diseases that can be carried by Mosquitos."Sting allergy" is pulled because it can be caused by Wasps or Bees. "Lyme Disease" is pulled because it is carried by Ticks.

Insects that don't carry diseases like Butterflies and Crickets and diseases not caused or carried by insects like Depression and Arthritis are excluded from the results.


When you use AND in a search engine, all of the terms are treated equally. You do not need to put your terms in order of importance.

Practice: Using AND

Form a question about two topics (e.g. Allergies AND Sleep) about what they have in common or how they influence each other.

Do a search for one topic (e.g. Allergies). Note the number of results and how relevant they are to your question. Do another search for a different topic (e.g. Sleep). Note the number of results and how relevant they are to your question.

Next, do a search combining both topics (e.g. Allergies AND Sleep). Does the number of results increase or decrease? Are the results more relevant to your question?


Search limiters/filters restrict the number of results so they are more precise.

What are search limiters?

Search limiters/filters eliminate articles that do not fit your criteria.


Common search limiters/filters include Date Published, Language, and Article Type. Most databases have limiters/filters that reflect the needs of its literature. As health literature databases, CINAHL limiters and PubMed filters include patient information such as Age and Sex.


Click here to learn about CINAHL's search limiters.

Click here to learn about PubMed's search filters.

Many health science research projects will only seek to focus on articles from the past five or so years. Limiting you search based on publication date before finding an article that falls out of this date range is a good habit to form.


Controlled vocabulary is the use of search terms specific to a database.

What are subject headings?

Let's say you want to do a search on the thing that you breathe through and sticks out of your face. Normally, you'd say “nose”. But there are different ways to say "nose", like “schnoz” or “sniffer.” Although we know that “sniffer” means the same thing as “nose”, it is not a professional way of saying it.

Medical professionals are more likely to say "sinuses" or "nasal passages" more than "sniffer", so it is wiser to use the term "sinuses" in a health literature search.

CINAHL and PubMed have these terms built in so that you don't have to guess what a professional author would use as his description. Click on the links to see how you can use this subject headings to narrow your search by database.

Click here to learn how to use subject headings in CINAHL.

Click here to learn how to use Medical Subject Headings in PubMed.


Sometimes the clinical terms don't match the database's terminology. Refer to the database's subject headings search guide for help matching terms.

Practice: Subject Headings

Come up with a word you hear every day. Write next to it the different ways that a professional says that same word.

Search using your everyday word and note how many results you get. Do another search using one of the professional terms you came up with. Did the number of results increase or decrease? Are the results more relevant?

Subject Guide

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David Nolfi


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