Why do we need to conduct a literature review? and what are the differences between a narrative literature review and a systematic review?

We need to conduct a literature review for several reasons:

1. To gain a deep understanding of the current state of knowledge on a topic.
2. To identify the gaps in the current research that can be filled by new research.
3. To provide a context for the research being conducted.
4. To justify the need for the research.
5. To avoid duplication of previously done research.

Now, let's discuss the differences between a narrative literature review and a systematic review:

1. Purpose: A narrative review provides a broad overview of a topic, while a systematic review answers a specific research question.

2. Methodology: In a narrative review, the author selects and discusses relevant research based on their expertise and judgment. In a systematic review, the author follows a strict protocol to search, select, appraise, and synthesize all relevant studies.

3. Bias: Narrative reviews are more prone to bias because the selection and interpretation of studies depend on the author's perspective. Systematic reviews minimize bias through a rigorous methodology.

4. Results: Narrative reviews provide a qualitative summary of the findings, while systematic reviews can provide a quantitative summary (meta-analysis) if the included studies are similar enough.

5. Reproducibility: The steps followed in a systematic review can be replicated by other researchers, which is not the case with narrative reviews.