PICO is a device to help ask good clinical questions, and it can also be used to help focus and search databases for peer-reviewed articles that answer those questions.

Most clinical research develops from an idea or scenario like the following:

You are a nurse working with a mother and her daughter, who suffers from epilepsy. The mother is aware that North Dakota has legalized medical marijuana and wants to know if that would be a safe option for her daughter. Apart from basic news stories, you haven’t heard much about medical marijuana and decide to investigate.

We can use PICO to pull out the keywords that will help us search.


On the table below, you can see what each letter in PICO stands for, and how to use that to develop keywords from the scenario above. Once keywords are identified, it is important to also think about some synonyms or related concepts to also try when searching.

  P I C O
Stands for: Patient, Population or Problem Intervention Comparison Outcome
Keywords: Female, child, epilepsy Medical Marijuana NA Safety
Synonyms: Pediatric, seizures, seizure disorder Cannabis, cannabidiol NA Adverse Effects

Things to Remember

  • Not all questions are about therapeutic interventions. If you’re asking an etiology question, for example, “Do mothers who smoke compared to mothers who don’t smoke have babies with different birth weights?” the I keyword will be smoking and C would be not smoking. It may be easier in those instances to think of I and C as experimental and control variables.
  • Comparisons may not always exist, as in the table above. Or they may be something understood, like standard of care. Or it may be placebo.
  • Outcome should be something that can be measured, so instead of “efficacy,” think of how that can be measured: days in the hospital? Tolerance? A particular result from a lab test? Patient satisfaction?
  • If you can’t think of any synonyms right away, look for other terms that come up as you are searching and then add them to the list of search terms.

Putting it All Together

Once you have your keywords developed, then you can decide where you want to search. If you’re not sure, check out one of the library’s subject-specific research guides. When you start searching, use 2-4 of the first keywords that you came up with. Evaluate the results, and change your search using other terms and database filters as needed. Check out these tutorials for further information:

  • Database search bar tips
  • PubMed