From the review:
"There are several limitations to the analyses that the authors acknowledge. The small number of available studies to include in the meta-analysis and their significant heterogeneity speaks to a paucity of overall evidence in this area and substantially complicates the interpretation of their pooled estimates. In addition, given the relatively consistent findings across studies and the difficulty in combining their results using meta-analytic techniques, it is unclear whether combining studies that used such disparate methods provides incrementally more additional information than the individual studies alone."
Of the nine studies, only one has a decent sample size. The studies can't be aggregated or compared. The rest of this meta-analysis is just padding.