Moderate or large effect size
For our review, we upgraded evidence for large or moderate effect sizes. For example, our review included two studies that examined through univariate analyses whether family history of headaches predicts migraine persistence. Monestero and colleagues  reported a significantly large effect (odds ratio = 6.2), while Ozge and colleagues  also examined the same relationship and reported a small-moderate effect size (odds ratio = 2.08). Collectively we felt these effect sizes were large enough to warrant upgrading the evidence, indicating that the relationship between family history of headache and persistence probably exists.