Do all systematic reviews include a meta-analysis?

Systematic reviews and meta-analyses are related but distinct methodologies in research. A systematic review is a comprehensive survey of existing literature on a specific question or topic. It involves a rigorous search for relevant studies, assessing their quality, and synthesizing the findings. A meta-analysis, on the other hand, is a statistical technique that combines data from multiple studies to generate a pooled estimate of effect.

Because systematic reviews can vary in their scope and the types of studies they include, not all systematic reviews will conduct a meta-analysis. For instance, systematic reviews might summarize studies that are too heterogeneous in terms of design, population, or interventions to meaningfully combine the data. Additionally, if adequate data or studies are not available to warrant a meta-analysis, the review will simply present a narrative synthesis of the findings.

Thus, while a meta-analysis can enhance the systematic review by providing quantitative analysis, it is not a necessary component; some systematic reviews may only present a qualitative synthesis of the included studies. This distinction is crucial in understanding the purpose and functionality of systematic reviews and when they might incorporate a meta-analysis.