The Library: Psychological Therapies

Develop a search strategy

Once you have decided on a topic for your systematic review, you will need to develop a search strategy. This involves:

• Breaking down your topic into the keywords and phrases that you will search for
• Identifying any relevant synonyms (words that mean the same thing) for your keywords. For example, if one of your keywords is nutrition, you may want to include similar words such as dietary or food intake.
• Thinking about advanced search techniques you could use, including phrase searching, truncation, or Boolean searching.

For more information on developing a search strategy, see our guide to finding information.

Below you will find an example search log document to show how you could plan and keep track of your search. The PDF version has been partially filled in to show what the completed search log would look like. The Word version is a blank copy which you can download, edit and customise.

Where to search

Systematic reviews are usually carried out in academic databases. You can find a list of key databases on your subject page, or a list of all library databases in our Databases A-Z.

You can test out your search strategy in different databases to see how effective the search is and whether the database contains relevant information for your topic. Bear in mind that each database works slightly differently, so you may need to modify your search for each database.

You should search multiple databases (usually at least 3) for your systematic review in order to collect a wider variety of information.

Citation searching is often used in systematic reviews. Citation searching means following up references or citations. You can do this by looking at the reference lists of articles you have found, by using a citation based database such as Scopus, or in Google Scholar. 

Managing your results

Doing a systematic review means dealing with a large number of search results. It’s important to have a system for organising your results. This means that all of your references should be stored in one place, along with information on which results came from which database. You will need this information for documenting your search (more on this below) and for referencing when you write up your systematic review.

You may wish to use a reference manager such as Zotero or EndNote. The advantage of using a reference manager is that they usually have a plug-in for MS Word which allows you to insert saved references and format them in the correct referencing style for your subject.

Documenting your search

The literature search for your systematic review needs to be documented in detail, so that anyone could replicate your exact search using the details you have provided. Remember to keep track of:

• Which databases you used
• The exact search strategy you used in each database
• Any filters or limits you put on the search e.g. publication dates
• The number of search results you found in each database
• Any additional search results you found without using a database, e.g. grey literature or articles you found by citation searching.

One way to document your search process (as well as the rest of your systematic review) is by using the PRISMA flowchart. You can use this template flowchart to record exactly how you carried out your systematic review, and include the flowchart as an appendix.

Narrowing down your results

In a systematic review you will need to be very selective about which sources are included in your final results set. Narrowing down your results is an important part of the process. This is often done using inclusion criteria: a list of requirements your results must meet in order to be included in the final review.

Some examples of typical inclusion criteria are:

• Research must focus on a specific population (e.g. women, footballers, diabetics)
• Research must have been carried out in a specific country or area
• Research must have been published within a specific time frame

Sometimes exclusion criteria are also used to rule out results, e.g. if the research was not carried out in the specified time frame it would be excluded from the results.

There are three main ways to apply your inclusion/exclusion criteria:

1. Using filters and limits in the database search (e.g. date limits)
2. Using keywords within the search (e.g. including keywords such as diabetic if you want to focus on people with diabetes)
3. Sorting through your results and filtering out items which do not meet your criteria. This can be a lengthy process. Remember to document how many results from each database you have included or excluded (e.g. using the PRISMA flowchart).

Critical appraisal

Once you have a set of results which meet your inclusion criteria, the next step is critical appraisal. This means carefully examining the quality of the studies you have chosen and identifying any potential issues with the study design or reporting of results.

There are many critical appraisal tools available to help you do this, such as CASP checklists. A completed CASP checklist for each article could be included in your appendices.

Only the articles which meet your critical appraisal standards should be included in the final review. Again, remember to document how many articles were ruled out due to critical appraisal.

Synthesising the evidence

By this stage you should have a final set of articles which meet your inclusion criteria and are of a high standard according to your critical appraisal. The next step is to read each article carefully and consider the findings and what they mean for your research question. When writing up the findings of your systematic review, think about:

• How much evidence is available and is it sufficient to answer your research question? 
• Are there any gaps in the literature where further research might be needed?
• What are the strengths and weaknesses of the studies you have included?
• Overall, what conclusions can you draw from the evidence you have found in order to answer your research question?

Check your module handbook or assignment brief for any specific guidance from your lecturer on how to write up your systematic review. You could also read some existing systematic reviews to get an idea of the typical structure and layout. An example of a published systematic review is linked below.