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Developing a Search Strategy

Developing a search strategy is the starting point for your information retrieval. Depending on the type of project you are completing - whether you just need a few articles for a class assignment or you need to complete a systematic search for your thesis - the level of advanced searching you use may vary, but the principles of a well structured search are the same. 

Use PICO to help structure your search and avoid searching frustration where ever and however you chose to complete your search! 


PICO is a commonly used tool to help break down the searchable elements of your research question. This helps to structure your search so that essential components are not missed and can help to enhance the relevancy of your search results. PICO is an acronym for: 

Population / Patient / Problem 

What are the most important or defining characteristics of the group, person, or problem you are interested in? Do your patients have a specific condition? Are you interested in disease incidence in a specific sex? Or special population group, such as immigrants or indigenous peoples? Are they a certain age - children, adults, elderly?

The more details you can provide, the more potentially relevant your results will be.


What is the treatment, technology, program, or initiative you are interested in applying? Try and be as specific as possible and have some definitions at the ready. For example, if you are investigating "Diet" as an intervention, what type of diet? Low-carb? Keto? Restricted? Vegetarian?  Vegan? What about dietary supplements? Vitamins and minerals? How do you define and understand the concept of "Diet"? 


What is the direct comparison to your intervention? Don't worry if you don't have one, this PICO element is often left off unless there is a specific comparison. For example, calcium from food intake vs calcium from vitamins/dietary supplements. 


What are you hoping to improve, measure, or evaluate? Reduce disease incidence? Manage or reduce symptoms? Improve systems and ways of working? 

PICO Example

Let's take this research question and break it down using PICO: 

Among elderly long term care home residents with depression, are therapy animal visits effective for managing or reducing depressive symptoms? 

Population - Elderly residents of long term care facilities who have depression

Intervention - Therapy animals

Comparison - None

Outcome - Manage or reduce depressive symptoms

In this example, more work is needed to define a couple of elements for the search. How old are "elderly" residents? 60+? 65+? What types of therapy animals will be included? Dogs? Cats? Horses? Rabbits? Other? 

Thinking about definitions and the structure of your search early on in your process can help to avoid frustration later on with either too many or too few results. 

Variations of PICO and Alternatives

PICOT can be used when a time element plays an important part in your research question: 

SPIDER is a variant that is often used in qualitative research: 

Not sure which would be best? 

Boolean Operators

Booelan Operators Venn Diagram


AND - Combines different concepts, narrows your search. Used to combine P AND I AND C AND O.

*This is usually the default operator of a database so it will automatically AND your terms unless you tell it otherwise. 

OR - Combines unlike terms, broadens your search. Used to combine your various keywords OR synonyms OR subject headings for a single concept. 

NOT - Excludes certain terms, narrows your search. USE WITH CAUTION! NOT is often used poorly by searchers and can eliminate potentially useful articles from your search. If you are struggling with relevancy in your search results, try working on refining your search concepts or consult with a librarian for help.