Skip to Main Content

Systematic Reviews: Step 3: Planning your search strategy

Subject Guide prepared by QUB Subject Librarians that will help you decide if a systematic review is right for your project, and guide you through the systematic review process
Planning your search strategy

This page contains useful tips and guidance on planning your search strategy, and adapting it for the various databases that you will need to search.

What is a search strategy?

A search strategy is a set of search terms combined in such a way to maximise the number of relevant records retrieved in a database search. 

Designing a search strategy is the first step in effectively reviewing the literature in your area of interest. If you don't use the correct terms or don't combine them correctly, you will either not get enough relevant results, or you will be overwhelmed with a large number of irrelevant records.

This page will guide you through the search strategy process, allowing you to create an effective search strategy that you can use to find relevant journal articles for your topic.  

Note that designing an effective search strategy can be time-consuming, so make sure you allow enough time for this part of your research!

Books on literature search skills

The Library has many books to help you with literature searching and designing your search strategy. Here are just a few that you might find useful; try the Library Search for the full range of titles. 

Print books
Make sure you understand your search question

Ensure that you have a clear understanding of your research question and its key components. You may want to use a research framework to help structure your question. Some examples are:

  • PICO (medical and healthcare reviews) - Population, Intervention, Comparison, Outcomes
  • SPICE (qualitative reviews) – Setting, Perspective, Phenomenon of Interest, Comparison, Evaluation
  • SPIDER (mixed methods reviews) – Sample, Phenomenon of Interest, Design, Evaluation, Research type
  • PCC (scoping reviews) – Population, Concept, Context

Steps to formulating your search strategy 
  1. Extract the main concepts from your research question. If you have used a research framework such as PICO, you may want to use this to help you to identify the main concepts. However, depending on your topic, you may not need to search for every component eg you may not have a comparison or you may choose to omit searching for the ‘outcomes’ if you don’t know in advance what the outcomes are.
  2. Bear in mind that the more concepts you search for, the fewer results you will get. You need to search for sufficient concepts to pick up relevant articles, but not so many that you risk missing out on relevant results. It is better to start with fewer concepts and then examine the results. You can always add another concept if you are getting too many irrelevant records.
  3. Once you have decided what concepts you want to search for, you will need to expand your keyword list: use synonyms, related terms, or alternate word forms for each concept. Consider plurals, different spellings, acronyms, or abbreviations that researchers might use. Eg Assess the effectiveness of cognitive behaviour therapy in the treatment of adolescents with eating disorders. The concepts you would search for are cognitive behaviour therapy, adolescents and eating disorders. You can then think of all the terms that could be used to describe each of these concepts. Constructing a table detailing each concept and its associated related terms can be helpful. You will probably come across additional terms as you peruse the literature so you should keep adding these to your table as you go along:
    cognitive behaviour therapy adolescents eating disorders

    cognitive behavioural therapy

    cognitive behavior therapy

    cognitive behavioral therapy








    young person

    young people

    young adults

    eating disorder

    anorexia nervosa




    avoidant restrictive food intake disorder


  4. Examine your keywords to see if you can streamline your search by using search operators such as truncation (for word variations) and word proximity. 
  5. Once you have a list of keywords and phrases, combine them using appropriate Boolean operators (eg AND, OR, NOT) to create search strings. Use AND to combine different concepts, OR to include synonyms or related terms, and NOT to exclude specific terms. Use NOT with caution as you can exclude relevant references eg searching for children NOT adolescents will exclude articles that cover both age groups.
  6. Brackets are used to group related keywords together in a search string; this ensures that the search within brackets is performed first. Eg:

(cognitive behavio* therapy OR cbt) AND (adolescen* OR teen* OR young person OR young people OR young adult*)  AND (eating disorder* OR anorexia nervosa OR bulimia OR orthorexia OR pica OR avoidant restrictive food intake disorder OR arfid)

NB you will need to adapt this initial search string for each database as they have different syntax and search features (see box below).

  1. Test your search strategy in a pilot database (select the key database for your subject) and review the results. Evaluate the relevance of the articles and note any additional keywords or subject headings that emerge. Refine and iterate your search strategy accordingly to improve the precision and recall of your search results. If you aren’t getting enough results, you may wish to remove a concept or use broader search terms. If you are getting too many results, you may wish to add a concept or use more specific terms.
  2. Remember formulating an effective search strategy can be time-consuming; it is an iterative, rather than a linear process and you won’t get it right the first time!

Adapting your initial search strategy for different databases
  1. Determine which databases are most appropriate for your research question. Different databases cover various disciplines, so choose the ones most relevant to your topic. 
  2. Understand the database: Familiarise yourself with the documentation and search capabilities of the specific database you're working with. Different databases may have variations in syntax, supported operators, and search features so you will have to adapt your initial search string accordingly. Eg
    • Exact phrase matching - “positive reinforcement” in the Web of Science ; {positive reinforcement} in Scopus
    • Extra character - orthop?edic in Ovid Medline; orthop$edic in the Web of Science 
    • See Database keyword search operators quick guide for more information on the search options available in key databases
  3. Use controlled vocabulary in addition to keyword searching, where available: Many academic databases use controlled vocabularies or subject headings to index articles eg Medline, PsycInfo, Cinahl. Identify relevant controlled vocabulary terms that match your research question. For instance, in PsycInfo, the term cognitive behaviour therapy has the subject heading cognitive behavioral therapy. 
  4. Find out which fields are being searched in the default 'unqualified' search in each database. Consider restricting your search to specific fields if this is more appropriate for your needs eg title and abstract
Planning your search strategy template

You may find it helpful to use the following blank Word document template to help plan your search strategy (see the second document for a completed example):

Which databases to use

If you are already familiar with some databases which are relevant to your research question, you can consider using those in the first instance. The best place to source databases is through the Library pages where your subject librarian will have listed all that are useful and available along with information about each.   

Google Scholar is often considered to be a starting point but for scoping reviews your supervisor will need to know that you have searched for peer reviewed materials. The Library subscribes to databases which index peer reviewed and other recognised categories of scholarly sources.  

If your research question is multi-disciplinary you may also need to select databases from other subject areas.   

The Library Article Search searches all of the journals which there are subscriptions to. It is a good option to search across all subject areas though it very much depends on your topic. To avoid being overwhelmed with results, you can ask your subject librarian for help with selecting databases.

Types of literature  

In addition to peer-reviewed journal articles, you will need to consider grey literature. This includes conference papers, papers in process, pre prints, theses, official publications, and other non commercially published materials. The Library’s Subject Guides provide access to a range of sources for this form of literature.  

If you need additional support with your search strategy, you can contact your subject librarian.

Advanced searching

With a list of databases and your search strategy ready, you can now test the search strings by typing them into the database and checking they work with the syntax matching the database requirements. If this appears successful then you can carry out the search formally, applying date and publication type criteria, followed by screening and saving your results a outlined below. 

Each database will allow you to decide where you want your search terms to be found by selecting one or more specific metadata fields e..g. this is an image of the first page of an article. 


Databases identify all these sections of an article separately (meta data fields) and allow you to then choose which field(s) to search. 

Search strings developed with natural and academic language are usually pointed at the title, author, keyword and abstract fields. 

Databases also have a subject index which is described in Useful search tips in Step 2. It is important to consider searching with subject headings and you may find it helpful to do so as a separate search.  

Complementary searching activities

It may be the case that you will need to pursue the following additional searching activities in order to locate pertinent materials:

Hand searching

Some journals and other research output may not have been indexed in an online databases and only available to you in print format. This means you will need to search through the printed volumes by hand to make sure you haven't missed any relevant research.

Citation chasing

When you read articles you'll see reference to other research which you will need to source.

Contacting relevant researchers

Where research is ongoing or you wish to identify whether the authors of works are still active in the area you may wish to contact them. They may have primary unpublished data relating to the studies which you need.

Inter Library Loan Service

Where it has not bee possible to gain online full text access to articles, book chapters or reports, you may wish to source them through the Inter Library Loan service.