设计：随机双盲法观察。
很少有实验报道随机取样的方法。内含的试验方法的质量一般很弱。三种试验分别为随机取样、双盲法、安慰剂给样试验。
The methodological quality of included trials was generally "poor." Few trials reported methods of randomization. Three trials were randomized, double blind, and placebo-controlled.
方法：采取随机双盲对照观察法。
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