A new paradox in random-effects meta-analysis

Abstract: Meta-analysis is an important tool for combining results from multiple studies and has been widely used in evidence-based medicine for several decades. This paper reports, for the first time, an interesting and valuable paradox in random-effects meta-analysis that is likely to occur when the number of studies is small and/or the heterogeneity is large. With the incredible paradox, we hence advocate meta-analysts to be extremely cautious when interpreting the final results from the random-effects meta-analysis. And more importantly, with the unexpected dilemma in making decisions, the new paradox has raised an open question whether the current random-effects model is reasonable and tenable for meta-analysis, or it needs to be abandoned or further improved to some extent.