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(a,b) Funnel plots illustrating the publication bias in overall PPD reduction in SM and PG studies, respectively; (c,d) funnel plots illustrating the publication bias in overall CAL gain in SM and PG studies, respectively. Each circle represents a single included study, the y-axis and x-axis represent the standard error of the effect estimate and the results of the study respectively and the graphical plot resembles an inverted funnel with scatter due to sampling variations.
