PICO for Extracting Essential Search Terms
A number of acronyms have been developed as tools to determine the essential search terms for a topic in literature reviews.
Please use the links below to explore ideas for identifying key words for your search!
PICO is commonly used in the Health Sciences for clinical interventions:
P = Patient / Population
I = Intervention
C = Comparison
O = Outcome
This acronym has been adapted and others developed for the reviews in other disciplines.
A sample of PICO variations include:
PEO - Population / Exposure / Outcome (see UNC Greensboro Guide)
PICo (Qualitative Studies) - Population or Problem / Interest / Context (see Murdoch University Guide)
SPICE (Social Sciences) - Setting / Perpective / Intervention / Comparison / Evaluation (see Murdoch University Guide)
Subject Headings: PubMed MeSH and CINAHL Headings
What are Subject Headings
A important part of the research process is knowing how to find and use controlled vocabulary. Controlled vocabularies are used by databases as a way to organize knowledge for subsequent retrieval.
Subject headings or terms, which are descriptive words assigned to an article by a database, are a common way databases use controlled vocabularies. These subject headings denote the item's subject or main themes. Articles with similar themes, or about similar subjects, will be classified together under a very specific subject heading - instead of scattered under multiple different synonyms or searches. Searching with subject headings allows researcher to focus in on all relevant research with one search term or phrase.
Be aware that searching by subject term is different than keyword searching. Here are some differences:
| Keywords | Subject Terms |
| Natural language used to describe your topic | Controlled vocabulary defined by each database to describe the content of an article |
| Great place to start searching for articles on your topic as keywords are flexible | A more advanced search method as you need to know the exact subject heading |
| Databases will default to search for keywords anywhere in the record | Database only searches for terms specifically matching in the "subject heading" field |
| May result in irrelevant articles | Results are usually very relevant to topic |
| May result in too few or too many articles | Can use subheadings to further hone in on a subtopic |
The following video nicely outlines these differences
How to Find Medical Subject Headings (MeSH) in PubMed and CINAHL Headings
Databases commonly provide a way to search for subject headings through their thesauri. Please note that subject headings differ across every database, therefore you first must look up the exact subject term for the specific database you are using.
While the way to find and use the thesaurus to identify subject heading is fairly similar across databases, there are a few differences. As such, there are videos for our two main database platforms - PubMed and CINAHL.
- PubMed Subject Search Introduction to MeSH
- Using CINAHL/MeSH Subject Headings (below)