Following calculation of the cross-sectional ES, the corresponding author from each study was contacted via email, with two exceptions. In Cardenas et al. (2005), the obtained ES was simply compared to the ES published in the original report and found to be very similar. For Mechtcheriakov et al. (2007), a valid email address for the corresponding author could not be found. When contacting authors, the ES was presented along with a request for the author to evaluate it in light of his or her expertise on the study. The 12 authors who responded to this request indicated the acceptability of the calculated ES. In addition, authors were contacted to confirm the independence of samples in cases requiring clarification.
