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Dissertation Subject Guide

including systematic reviews, literature reviews and scoping reviews

Getting your search strategy right

Think carefully about the search terms and techniques you use. Remember that the databases will just literally search for the terms you have added.

You will be expected to at least use some or a combination of the techniques below to help you create a comprehensive search strategy for your dissertation. 


Finding the right words and phrases to search for can be difficult and time consuming.

Think of different words or phrases that can help your search. This is called synonyms. This may mean that your search includes records that you might not have found before or widen the scope of your search to include those records that have used different words than you initially searched for.


nurse practitioner advanced practice nurse, ANP, NP
care home residential care, nursing home, residential home, elderly care
mental health mental illness, mental disorder, psychiatric illness

If you're struggling to think of other words/phrases:

  • try RCN clinical topics - (not comprehensive but can be a good start
  • Using Advanced Search in CINAHL or Medline automatically creates synonyms as soon as you start typing your key term
  • When you find a good research article look at the keywords used in that research. This is normally found underneath the abstract

Once you have your different words and phrases you can combine them using Boolean techniques to make your search even better. Boolean are simple words (AND, OR, NOT etc.) used to combine or exclude words/phrases in the search. Use the tabs below for examples and explanations.

Boolean Techniques


Using AND between keywords narrows your search results from just a keyword search

Covid-19 vaccine basic keyword search
Covid-19 AND vaccine will combine terms together and reduce result numbers
Covid-19 AND vaccine AND health promotion can be used more than once in same search



Using OR extends your search out which retrieves more results. Works very well with very similar keywords and means you're not missing out on any relevant research.

Covid-19 OR Coronavirus will search for same term simultaneously, giving more results
Covid-19 OR Coronavirus OR pandemic can be used more than once in same search



Use NOT to exclude results that you're interested in and reduce the number of records retrieved.

Covid-19 OR Coronavirus NOT SARS will exclude SARS records from search


Phrase searching works really well on all databases. Works well for a phrase that can also work as separate keywords.

Vaccine hesitancy will search for vaccine and hesitancy as separate words extending your search out and showing many irrelevant records with records with vaccine and records with the word hesitancy.
"Vaccine hesitancy" will retrieve records with phrase only
Covid-19 AND "Vaccine hesitancy" AND "health promotion" can be combined with other search terms


Truncation can extend your search out to ensure you're not missing out on any relevant records. Works with words with different endings. Go to last letter of word before ending changes and add *. Here's some examples:

nurs* will retrieve records with the keywords nurse, nurses, nursing
dentist* will retrieve records with the keywords dentist, dentists, dentistry
manag* will retrieve records with the keywords manager, managers, management
vaccin* will retrieve records with the keywords vaccine, vaccines, vaccination, vaccinations


You can use parentheses/nesting to build a search with a combination of Boolean Operators by using (...). The search inside the (...) is always done first so this can affect your search results. 


(Coronavirus OR Covid-19 OR pandemic) AND vaccine  keeps synonyms together
(Coronavirus OR Covid-19 OR pandemic) AND (vaccin* OR immun*) can be added more than once to each search
((Coronavirus OR Covid-19 OR pandemic NOT SARS) AND vaccine 

You can also use parentheses within parentheses. 

Some databases allow for searching for words within the same sentence or within a defined number of words within one another e.g.

SAME Covid-19 SAME "vaccine hesitancy" using SAME will search for Covid-19 and "vaccine hesitancy" in same sentence
W- Covid-19 W3 "vaccine hesitancy" using W3 will search for covid-19 within 3 words of "vaccine hesitancy" (change the number for limit of words between phrases/keywords e.g. W5, W7.)
NEAR Covid-19 NEAR  "vaccine hesitancy"  using NEAR will search for covid-19 within the databases definition of NEAR to "vaccine hesitancy"




Boolean Operators

MeSH & CINAHL Headings

What are MeSH Headings and CINAHL Headings?

The Medical Subject Headings (MeSH) thesaurus is a controlled and hierarchically-organized vocabulary produced by the National Library of Medicine. It can help you when searching for biomedical and health-related information. MeSH includes the subject headings appearing in MEDLINE and PubMed. For more information see the Welcome to Medical Subject Headings.

CINAHL Headings is a controlled vocabulary of subject terms. It works very similarly to MeSH Headings. Subject terms are assigned based on article content, allowing you to create a targeted search.

However, when are searching systematically, remember that the controlled language may differ between MeSH and CINAHL headings. And these Headings will not work in the same way in other databases such as Scopus, Web of Science or ASSIA.

How do I use MeSH Headings and CINAHL Headings?

See this guide - Using CINAHL/MeSH subject Headings
Or Video from Ebsco - Using the CINAHL/MeSHSubject Headings Feature in EBSCOhost

Pubmed tutorials - Learn about Medical Subject Heading (MeSH)


Limiting your search can impact the numbers of research papers you find. Most databases allow you to narrow your search according to your chosen criteria. 

Common limiters (also called filters) include:

language - narrow down to English language

years - very much dependant on your subject and current research available. Keep to 5 - 10 years for most up-to-date research.

Be careful of filter/limit to country. You may find that research papers retrieved are not from that country but could mean that one of the authors is affiliated with a healthcare provider or University in that country. You might be better adding your given country to your searches instead.

Searching School

For the other searching videos in this series Searching School