The initial PubMed search yielded 216 records. Among them, 107 articles were excluded for not meeting our inclusion criteria: studies with no acupuncture group per inclusion criteria (n = 39), non-RCTs (n = 26), protocols only (n = 20), studies with no placebo acupuncture control group (n = 19), animal studies (n = 2), and a duplicate (n = 1) [18, 19]. Additional 53 studies included in a previous systematic review  of placebo-controlled trials of acupuncture were then added to the remaining 109 studies. One study  from the adopted list was replaced by its original trial as it was identified as an additional report . Two studies overlapping with our own search result were excluded, leaving a total of final 160 studies subject to invitation to share PILs.