Introduction

The systematic review and the meta-analysis are two closely related research processes that play a decisive role in the evaluation, synthesis, and interpretation of findings from different scientific studies. Their main objective is to provide an overall, reliable, and evidence-based conclusion regarding a specific research hypothesis or examined relationship, thereby supporting sound decision-making, particularly in the fields of health and social sciences. They constitute two sequential stages of a unified scientific process, aiming to produce valid and objective conclusions based on empirical data.

The Importance of the Systematic Review

The systematic review represents the first and foundational step of the process. It is a structured and methodical review of the literature that seeks to collect, analyze, and evaluate all relevant research pertaining to a particular question or phenomenon. Unlike traditional or narrative reviews, the systematic review follows predetermined protocols, applies strict inclusion and exclusion criteria, and ensures transparency and reproducibility of results. Its application becomes essential when the existing research data are numerous, contradictory, or limited, as it allows for the combination and comparison of results in order to extract well-substantiated conclusions. Moreover, it contributes to identifying gaps in the literature and provides direction for future research.

The process of a systematic review involves clearly defining the research hypothesis, establishing inclusion and exclusion criteria for studies, searching for and selecting the research to be utilized, and assessing their methodological quality. Finally, the results are summarized and interpreted to derive comprehensive and trustworthy conclusions. Systematic reviews that focus on limited and specific research hypotheses are considered particularly effective, as they allow for deeper and more specialized analysis.

Meta-Analysis as a Complementary Process

Meta-analysis constitutes the second stage and functions as the quantitative extension of the systematic review. Through statistical methods, it combines the results of multiple independent studies selected according to specific criteria, producing a cumulative and representative outcome. In this way, it enhances statistical power and the reliability of conclusions while reducing the likelihood of error that may arise from small samples or individual studies. A meta-analysis cannot be conducted independently of the systematic review, since it relies on the data collected and assessed through that prior process. The quality and validity of its results depend directly on the quality of the preceding review.

During the execution of a meta-analysis, the publication bias is first evaluated in order to detect possible distortions in the publication of results. Subsequently, the heterogeneity of the included studies is assessed to determine the degree of similarity or variation among them. Finally, through mathematical and statistical techniques, the results of the individual studies are combined to produce an overall effect measure that accurately reflects the true relationship between the examined variables.

Relationship and Interdependence of the Two Processes

The systematic review and the meta-analysis are interdependent and complementary procedures. The former provides the theoretical and methodological foundation, while the latter offers statistical validation and quantitative precision. Their combination represents the most powerful tool in evidence-based research, ensuring completeness, validity, and objectivity. Meta-analysis enhances researchers’ ability to identify consistent patterns and trends across different studies, offering a more comprehensive and integrated understanding of the phenomenon under investigation.

Conclusions

In summary, the systematic review and the meta-analysis constitute two fundamental pillars of scientific methodology. Through their combined application, the validity of conclusions is ensured, and the reliability of scientific knowledge is strengthened. Working in synergy, these two processes contribute to evidence-based decision-making and promote transparency, consistency, and the advancement of research. Thus, they are invaluable tools for every researcher who seeks to base their conclusions on solid empirical data, leading science toward higher levels of accuracy and credibility.