Having a clear, manageable topic for your research is key to research success.   As you think about your topic, consider how you can specify the main concepts that are part of your topic. For example, if you are interested in whether vegans have trouble getting enough vitamin B12 in their diets, you can think about the “building blocks” of your question as:

A search like this will find results about vegans and/or vegetarians that at least have a mention of B12 in the article. Doing a broad search at first and then adding more terms or limits to narrow your results down often makes for much less frustration.

Think About Keywords

Keep in mind that there may be more than one term that means the same thing, or something very similar.  For example:

CVD or cardiovascular disease or coronary disease or heart disease

teen or teenager or adolescent or youth

folate or folic acid

You will also find keywords to try in your readings and in your notes from class.  Synonyms are useful when you’re doing searches.  

Consider Descriptors (controlled vocabulary)

Many databases also use specific keywords or terms called descriptors that are assigned to articles on that topic.  Once you know the descriptors for your topic it can make it easier to pull all articles on the same topic together at the same time.  In many cases the descriptor will be the medical term – just be aware that terminology changes.   You will find descriptors (often called Subject Headings) in database search results by looking at the individual records for articles.  Many databases for the health sciences (PubMed, CINAHL) use the Medical Subject Headings (MeSH terms), so becoming familiar with the MeSH terms associated with your topic will be useful.  To locate specific MeSH terms in PubMed, use the “MeSH” dropdown option from the search box.  Click here more info about PubMed and MeSH terms.  The PubMed Tutorial from NIH is an excellent way to learn how to construct effective searches in PubMed, or look at the NIH MeSH Tutorial for a quick overview.

Once you identify the terms (keywords or descriptors) applicable to your question or topic, put them together with Boolean operators such as AND (for more precision in your search), OR (to enlarge the pool of results when more than one situation is concerned), or NOT (to exclude possible elements that might jeopardize quality for quantity in your results.  (Be careful using NOT though, as you may exclude useful results!)

For example, if you want to know “what are some common dietary interventions or treatments for overweight children who have developed type 2 diabetes?” your terms might be

And your search might look like this:

Diabetes AND “type 2” AND (children OR adolescents) AND (overweight OR obese) AND diet

Or it might look like this (with MeSH terms in PubMed):

"Diabetes Mellitus, Type 2"[Mesh] AND ("Child"[Mesh] OR "Adolescent"[Mesh]) AND "Obesity"[Mesh] OR "Overweight"[Mesh] AND "Diet Therapy"[Mesh]

Going back to our vegans and vitamin B12 topic, a search to exclude any results about vegetarians would look like this*:

(Vegan NOT vegetarian) AND B12

(*However, remember any articles that contain BOTH vegan and vegetarian will be excluded from your results because we specified that we do not want the term vegetarian to appear in the results at all!)

Tip: Each database has its own thesaurus to organize articles on certain topics. Take a look at the database’s thesaurus to see if it uses a different term if your search does not yield enough results on your topic. 

Tip: Put quotes around search terms that are phrases (contain more than one word).  For example, placing quotes around “Mediterranean diet” will locate articles for you in the databases containing the phrase “Mediterranean diet” and should weed out all the articles where those words appear separately from each other (for example, an article about trying to be on a diet while on a cruise ship on the Mediterranean Sea!).