The methodological quality of each randomized controlled trial (RCT) was rated according to the Jadad scale (24). Points were awarded as follows: the study was described as random- ized, 1 point; the randomization scheme was described and appropriate, 1 point; the study was described as double blind, 1 point; the method of double blinding was appropriate, 1 point; there was a description of withdrawals and dropouts, 1 point. The maximum point-score available was 5.