What is a review of related literature (RRL)?
An RRL is an in-depth
examination of all recent research that is relevant to your current study and research question. An RRL involves
- Searching the literature (i.e., existing databases, preprint servers, and grey literature)
- Finding and reviewing studies that are related to your research question
- Understanding what has already been done on your research topic, what methods were used to investigate this topic, and whether there are any gaps, inconsistencies, or conflicts in the published evidence
An RRL is NOT
- A simple summary of every study conducted on a topic
- A commentary or opinion on a single study
- A statistical investigation that pools and re-analyzes data from multiple individual studies (this is called a meta-analysis)
Importance of a review of related literature (RRL)
Regardless of what research you’re doing or what type of study you intend to conduct, an RRL is very important. Here’s why:
- You become more knowledgeable: An RRL helps you get a holistic idea of the topic you are investigating, letting you gain knowledge from researchers far outside your immediate circle or even your country.
- You avoid duplicating previous work: It’s very frustrating to receive a rejection letter from a journal saying that a similar study has already been published and therefore your own research lacks novelty. A good RRL will help you avoid this and point you to what gaps you can try to fill in existing knowledge.
- You can design a better study: Suppose you’re investigating the relationship between alcohol consumption and depressive symptoms in postmenopausal women. You find that a few previous studies have included household size/household composition as a confounder. You speculate that the presence of younger children in the home may influence both alcohol consumption and depressive symptoms. Therefore, you also control for these variables, and you ultimately get a clearer picture of the relationship you are studying.
- You find out what works and what doesn’t: Maybe you want to investigate the relationship between physical activity levels and norepinephrine levels in adolescent boys. You find that previous studies have a lot of conflicting evidence. You realize that these conflicts arise because the studies used self-report instruments to measure physical activity. You therefore design your study such that physical activity is measured using a wearable device, which is more objective and reliable than self-reporting.
Purpose of an RRL
When you include an RRL in your thesis, dissertation, or research paper, it should serve the following purpose:
- Concisely summarize what is already known about the research topic, presenting only relevant details about previous studies
- Identify the strengths and limitations of key research on the topic
- Clearly articulate what are the gaps in existing knowledge about that topic: For example,
Thus, existing research strongly supports a relationship between hepatic steatosis and skeletal muscle mass index in men, but it is currently unclear whether this relationship exists for women.