Short answer: researchers conduct systematic reviews by following a planned, transparent method for finding, selecting, assessing, and synthesising all relevant studies on a specific question.
A systematic review is different from an ordinary literature review. It tries to reduce cherry-picking by making the search and selection process explicit. The review should be structured enough that another team could understand what was done and why.
The main steps
Researchers begin with a focused question. In health research, this may define the population, intervention, comparison, and outcome. Then they create a search strategy for databases and other sources. They screen titles and abstracts, check full texts, and apply inclusion and exclusion criteria.
Next, they extract relevant data from the included studies and assess risk of bias. If the studies are similar enough, the reviewers may conduct a meta-analysis. If not, they may use a narrative synthesis, explaining the evidence without statistically combining it.
Why transparency matters
The strength of a systematic review depends on its method. Readers should be able to see where the authors searched, what they included, what they excluded, and how they judged study quality. Without that transparency, a review can quietly become selective opinion.
A good systematic review does not guarantee a simple answer. Sometimes it reveals that the evidence is weak, inconsistent, or missing. That is still valuable. Knowing what is not known is one of the most useful outcomes of careful research.