How To Do Secondary Research or a Literature Review

Developing search terms starts with developing a research question. There are many ways to develop a research question, and your assignment may dictate which format to use, but the PICO framework is a very common format used in the health field.

An example research question using the PICO criteria:

Does group therapy [Intervention] lower the number of panic attacks per year [Outcome] when compared to drug therapy [Comparison/Control] for teenagers diagnosed with panic disorders [Population]?

After you establish a question, you can begin developing keywords for the four PICO criteria (or if you're not using PICO, the main themes of the question), including synonyms you can think of. It can help to break this up into a chart, like the example below. In this case, it's best to break up any compound criteria such as "teenagers diagnosed with panic disorders," into distinct concepts like simply "teenagers" and "panic disorder."

For a psychology literature review, searching both PsycINFO and PubMed are your best bets. Both of these databases are very comprehensive. There will be some overlap between the two databases and some articles will appear during both searches, but you can filter for duplicates if you use a citation management program like Zotero (see later box about citation management). Searching tips for both databases follow.

How to search PubMed in a systematic way 

1. Create a saved search for all of the terms that represent a concept

The most comprehensive way to search PubMed is to create a separate but comprehensive search for each of the terms related to the concepts (step 1), then combining all of those searches in a logical way (step 2). To do this, I would want to make one search string for all the potential terms used for each concept. I'll use the Intervention concept as an example. First, I will search for the first keyword I thought of to describe the concept, "group therapy."

Even though I searched just for "group therapy," the database interpreted my search in a different way. This is due to PubMed's algorithms. You can find the search details on the right side of the page: 

Because this is how the database interpreted my search, I'll want to copy and paste that into the upper search box. We'll look at why in a bit.

From here, I would continue like this, searching for each phrase of word that describes my concept separately. When done, go to the Advanced Search to see your history:

As you can see, the simple searches I entered have the same number of results as the more complicated, database code that I copied and pasted. The reason I did that is to preserve the actual details as run by the database. From here, I can combine the detailed searches by applying Boolean logic.  Because I want all possible terms that cover the same concept, the searches will be combined with OR. You can do this by clicking on the Add link next to searches 11 and 10, and separating by OR. Click search again and return to the search menu. There, you will have and you have one comprehensive list of all the terms related for one of your concepts (as number 12 below). 

Make sure to sign in and save this history to preserve it in case you need to make changes in the future. Click on the number of the search and choose Save to NCBI (if you don't have a free NCBI account, you will need to create one first):

Repeat this step for all of your concepts, combining each separate search into one comprehensive search for that concept and saving it.

2. Combine the concept searches logically

After you have created a comprehensive search for each concept, think about how the searches should be combined. Often, this will be simply combining all the concept searches with AND (so you get the overlap between all the terms), but not always.

For example, some researchers don't include textual searches for an age group as key terms; instead, they rely on the database filters for that. This is up to personal preference but you will likely have slightly different results depending on what you choose. 

For my sample question, I'm really researching two separate issues because I want to see both how group therapy works for panic attacks and also how drugs work, so that I can compare them. The reason I wouldn't want to search for ALL the concepts together in my example is that it's unlikely there are many articles explaining my exact issue (in other words, articles that compare the two therapies). 

To search for relevant articles about the intervention of group therapy question, I'd want to combine my comprehensive searches made for the Population, Intervention, and the Outcome concepts with AND by using the advanced search:

I click Search and end up with 184 relevant results. You should of course save this final search as well!

3. Modify as needed

If you think of other terms to include in your searches, you should modify each concept search individually and then re-combine them.

Other tips:

• Sign up for a free NCBI account. This will allow you to customize your search criteria, save searches and search history, and organize articles into folders.
• PubMed's search algorithm uses something called Automatic Term Mapping (ATM), which automatically groups phrases and searches different fields for a thorough search. This is useful for simpler searches or when you don't need to document search strategy, but for literature search documentation, it's best to look at the Search Details box, modify the search as needed, and record that as your actual search method.
• use Medical Subject Headings (MeSH) to help find targeted results. You can use MeSH terms and the corresponding subheadings to find targeted results.

Tips:

• In addition to using keywords, take advantage of the Thesaurus, which uses indexed terms. See more info about the index terms on the PsycINFO guide.
• Create an EBSCO account. This is separate from your MyIIT login and allows you to save search history, set up search alerts, and organize research.
• Avoid using quotation marks when searching. By leaving them off, the database will automatically search for slight variations of your keywords, such as plural versions or alternate spellings. 
• Using the "Peer Reviewed" filter will limit results to only peer-reviewed journal articles. This will make up the majority of your literature, but if you'd like to also find items like books or conference proceedings, consider leaving that filter off.
• Note that your search results will vary by using Limiters, such as Age or Population Group, will provide you with different results than by using keywords for the same concept.

How to search PsycINFO in a systematic way

1. Create a saved search for all of the terms that represent a concept

Similar to the PubMed strategy above, create a separate but comprehensive search for each of the terms related to the concepts (step 1), then combining all of those searches in a logical way (step 2). To do this, I would want to make one search string for all the potential terms used for each concept. I'll use the Intervention concept as an example. First, I will search for the first keyword I thought of to describe the concept, "group therapy." PsycINFO differs from PubMed because the search you enter is the search you get (except the database will apply slight variants such as British spelling, plurals, etc.). You can choose whether to search all fields or a specific field such as the Title (See the More Tips section if you'd like to use the database subject terms).

Repeat for all of your terms:

When you are done searching for each individual term separately, click on the Search History link underneath the search boxes. From there, first clear any terms left in the boxes above and then combine your searches using the checkboxes and the "Search with OR" link.

This will create a combined search, but unlike PubMed PsycINFO does not list the details of the words used, so it can help to immediately save and rename the search to something more descriptive. To save your searches, click on the search(es) you'd like to save and click on Save Searches/Alerts. You will need to make a separate EBSCO account to do this.

2. Combine the concept searches logically

Once you have created separate, comprehensive searches for each concept, then combine them following the same strategy listed above in the PubMed box but using the "Search with AND" box on the search history page.

3. Modify as needed

If you think of other terms to include in your searches, you should modify each concept search individually and then re-combine them.

As explained above, when conducting a comprehensive literature review, it's very important to use a systematic approach. This is especially important when submitting an article for publication, because you're often required to submit the search strategy you used. Instead of combining words/phrases into one search on the home page of the database, it's a good idea to use your Search History instead. This will help you be sure that your search terms are being combined properly and in the right order. See the links below for more background and alternative explanations: 

In general, PsycINFO and PubMed are better bets to use than Google Scholar when conducting literature searches, because the search fields and algorithms are much more advancec. PsycINFO and PubMed also employ actual human indexers that review and categorize articles, whereas Google Scholar relies on keyword searching alone, so it's easier to get more complete and relevant results in PsycINFO or PubMed. It's also easier to keep track of your search strategy when using PubMed or PsycINFO.

Using a citation manager requires a bit of a learning and adjustment period, but has a great payoff. Invest a bit of time to learn how to use one and you will benefit for the rest of your educational/professional career! Citation managers help you capture and organize references that you've found online, including the full text if available, and then help you to draft in-text citations and bibliographies. There are several available, but the library recommends Zotero if you aren't yet using a citation manager, because it is free, open-source, and very easy to use.

If you have a novel topic or one that has not yet been empirically studied extensively via research articles, you may need to supplement with dissertations, theses, or books.